Takes 90 minutes for me to drive to 'da cabin. In an average year, we spend roughly 60-70 nights at the cabin (we rarely go anywhere else on vacation).
If you don't have a specific location in mind, my advice would be to keep the time under 4 hours (2 is better).
Any longer than that, and you will likely not use it enough to warrant the expense.
If it takes 6-8 hours to get there, you will only likely go a couple times a year....at that point rent a place....its way cheaper.
Figure out the number of nights you would be able to stay there in a given year, and then divide the cost of buying a place by the number of nights.....it ain't cheap!