I'm quite new at budgeting and I would like to know if it's useful or important to save budgets from past years? And why? (I use Excel)

From a practical point of view I ask our clients to keep the budgets from past years at least the past 3 to 5 years. What I'm looking for as a financial advisor is the change in spending habits or additional sources of income. One of the great advantages of Quicken or QuickBooks or some of the other checkbook management programs is that you can print past years side-by-side to do the kind of comparison I'm looking for. By placing them side to side, my opinion is that they will allow you to project into the future with reasonable accuracy subject only to those nonrecurring items that may come up from year-to-year.  Most people have actually no idea where they spend money in this is the reason for extremely poor savings habits. I hope this helps and good luck