How to stay 'orange' ?
I study every day (really), but my oranges won't stay orange :\
I want to be solid, before trying a new lesson. So I've been going over old lessons, bringing them up to orange. Yesterday I almost had all orange for all the lessons I've worked, but today some really old lessons, near the beginning, are back to red or green.
My French tree (which I finished) is solid orange, and stays that way.
Should I forget the orange business, and just keep going on to new material?
Is there some setting I need to change?
If you feel you understand what you've learned, you don't have to gild lessons before moving on.
My rule of thumb: if you're doing new lessons and they're really hard or you're making a lot of mistakes/it's taking you a long time to get through a lesson, then you're probably going too fast and should slow down. If you're zooming through with no mistakes, then you could stand to go a bit faster. If you're making some mistakes on new lessons, but only on the new material, then you're probably going at about the right speed for you.
Duolingo tracks when you use hints or make mistakes, so if you are gilding but making errors, then your gilding won't last very well.
It's possible of course that you have some sort of bug; on any given skill, I have found that redoing the individual lessons and then doing a strengthen makes a skill very solidly gold. If you do this (without errors or using hints), and the skill still decays quickly, it's probably worth sending Duolingo a big report.
However, there really isn't any obligation to keep your skills gold as you go along, and if you are finding new skills are not too hard, then you can ignore your decayed skills without guilt!