How long should a car last? years vs miles

As long as you’ve kept up on maintenance, it should last awhile. Though, since it’s a Volvo, fixing things will be more expensive than a Ford or Honda.
If you do a lot of highway miles, you might consider buying a diesel car. If it’s around town, a hybrid will suit your needs best. Start looking now, get a feel for what you might want, figure a budget, then start saving.