Don't put off a trip to Alaska because everything isn't perfect, time available, money, as you may find out your stars never will align for going.
Excellent advice. I look at major trips sort of like starting a family. You question your timing and think you can't afford them but you manage. Flexibility is a must. IMHO there's two ways to look at budgeting:
1. Decide on a fixed amount and plan your activities, length of travel, etc., accordingly.
2. Decide what you want to do, how much it's going to cost, and put "X" number of dollars away weekly to achieve that goal. Requires discipline but not undoable.