The last Egg Quest is not easy if you don't have a dark patch. I went to Shillrigg Tiers in Groddle Forest to try for it. It, of course would be easier to have a Friend with a dark patch help me but I wanted to see if I could get it on my own.
I arrived at Shillrigg Tiers which has several Egg Plants. I choose the one on the left side of the door to Snool. I poisoned the plant and when it died I cleared, tended and then planted a new Egg Plant. here is how it went, Times are RW times. I also Petted when I Watered:
2:10PM - Poisoned
2:13PM - Cleared, Tended, Planted
2:19PM - The first Watering
2:26PM - 2nd Watering
2:34PM - 3rd Watering
2:39PM - 4th Watering
2:46PM - 5th Watering
2:48PM - Sudden Growth Spurt, Would not allow Pet or Water
2:51PM - 6th Watering
2:55PM - Egg stolen by intruder - NO QUEST FOR ME!
I don't know how long it would have taken to get the Egg but I was nearing one hour of care. I had Dust but did not use it because I was curious to see how long it would take to get the egg. In the end the person who came in used Dust and harvested the plant twice. I jumped in and also harvested twice but was unable to beat the thief to the last egg. When he left there were two eggs on the plant and I could not Harvest because I had met my limit of twice in a Game day. It was 11:38AM, Game Time. I still have yet to get this Quest but a Friend with a dark patch will help me. I did come close to learning how long it would take though. My guess is that it would have taken just about an hour of care to finally get the Quest with no boost from Dust.