I've only just started out with cake decorating (I've been self teaching since June) and have been getting a surprising amount of orders due to word of mouth.
People are asking for quotes on cake prices for as far ahead as August. I'm having trouble pricing cakes as it is without trying to guess how much they will be worth with 10 months more experience under my belt.

Do you guys have any advice? Should I just explain that my prices will have gone up by then, or tell them that the quote is only valid for x amount of time?

Thanks,
Mary

If you give a price quote that's based on cost + profit margin (where cost = the ingredient cost, labor cost, and anticipated per-order overhead), then you should come out ahead in future orders, since you will presumably be getting more efficient and taking less time to complete orders, which translates into lower labor costs and higher profit for you.

If someone signs a contract for a certain price you can't raise it later unless you have a clause in there that says that you can. I wouldn't sign a contract like that, though! If you're really worried about it, you could add a percentage to any quotes for cakes more than X number of months away, whatever you're comfortable with. If you raise your prices on a regular schedule you could base it on that.