Just taking a stab at when I think that the first person will have finished all the violets.
(and please take this as the fun that it is meant to be (tongue in cheek)... I know all the "Its not a race" etc etc.
My guess is that the first person will have finished all the current Candy Critters by June, 1st. 2050.

LOL!  Love your guess, Shelley. :)  I don't think it'll take that long, because we can rule things out as we go just as easily as we can rule them in.  We already have people who are pretty close to getting the violet of one type...that just leaves the other 6 to go. :)  I think the randomness is going to slow people down alot, as it's possible to know what you need and still not be able to attract the violet because you can't get the plant.  (Or, conversely, to know a particular plant won't work but still keep ending up with it in your garden.)  I keep thinking of the buildables and how hard it can be to get that particular part that you want.  As we narrow down the possibilities, the shape and color of plant we want is going to get more and more specific and, thus, harder to find.  Still, I wouldn't be surprised if someone has them all done within a month...but I also wouldn't be surprised if it takes longer!  (LOL!  I'm hedging my bets! :))

Fair enough Rachel.  When everyone is out of the house tonight, I am bringing out my huge whiteboard.  I have a few notes so far and will try to make some sense of them.  I was very chuffed when one of the positions has been revealed as one shape and colour correct!  I am looking forward to nailing that one.  And yes, I think I have overestimated a tad!

I think it'll follow a curve - at first every shape is new and there's something to be learned from every candy in our gardens (even if they attract nothing in any position, that shape can be eliminated ) so it'll look like things are going quite fast, but bits of information will be all over the place.
We can focus on hunting for particular shapes, so our hypothetical first (HF) checks all the shapes out first and gradually gets some kind of order and knows what every shape should be. Maybe some colours too.
Time taken:
(lets assume that HF got lucky and started out with 3 different shapes, after all that's what put her in the lead)
she tries them out with 3 different foods. 2/3 of a day on superfood (10 feeds) with plants in the order 123
the remaining 5 feeds and first 5 feeds of more sf with plants in the order 231
the remaining 10 of that second plate of each type with plants in the order 312.
2 days so far, then another day with the 4th type of food on each plate (or only 2) changing the order of the plants after every 5 feeds (total 10 or 15 feeds)
Total 3 days to get all the information about 3 shapes.
Repeat for the next 3 shapes.
No need to repeat for the 7th shape as it will be the one that fills all the gaps. That is if everything has gone to plan, but HF wouldn't be the first if it didn't.
So this bit takes - 6 days - lets say a week

Now the curve will bottom out, HF has got all the information on shapes, maybe a few colours. HF concentrates on one section at a time, hunting for the 3 shapes needed for that section (with another 3 growing as they wait in line to be tried out). She hunts for the 3 shapes for that section each day to replace yesterdays.
I'm not convinced there are only 7 different colours, but lets say there are. So on average 1 day in 7 she comes up with the right colour. In one week she's got the violet of that section.
There are 7 sections, so doing this with every section will take 7 weeks after the first week of finding shapes

Makes 8 weeks.

I dunno. Suppose HF actually totally randomly got the three correct colours and shapes, in the correct positions, with the very first three seeds she planted? Isn't that possible?!

Possible. but not probable.
It's also possible but even less probable that she'd have that luck for all 7 sections.
Then there's the outside possibility that she needs exactly the same set up for all of the violet ones, or at least some of them.

She might even finish tomorrow, but she wouldn't have coloured all her pics in.
Hmmmm define finish? Does she need to have attracted all the candy critters including the ones that will only come to a wrong colour.

I'll guess March 1st, I'm always surprised at how quickly people get through new things here.

I’ll guess May 1. 

The slow down in my opinion will be in hunting for the correct shape and then waiting for the chocolate to melt to see what color you get.

Even “buddies” will have to wait for growing time.

April 1st 2088 ...Most of us be expired so will no longer give a Hoot lol But if we leave Our garden with summit like this Post it in
( I Want it known Candies are BAD for ya Health  Intellect and making ya look stooooopid lol ) I leave this Land with one thought only FOR GAWD SAKE SOMEONE SOLVE IT lol And i really Luv CRISPS lol

lol Suzi.
I juat know this is the most fun thing I have done in Fairyland since the Fairytales.  I am always in aw of the few fae who zooooooom through quests and tasks. While I plod along at the back somewhere !