DoubleDonk, it's mainly money. I'm fortunate enough to hire from a group with no limits on how long you can take aircraft for. I could fly from Coventry to Wellesbourne and not take it back again for a fortnight if I really wanted to. I wouldn't of course, because it's not fair on the others.
I did intend to fly out to Welshpool for a weekend's walking last summer, but the possibility of being stranded and having to pay for accommodation was outside my budget limit. Unfortunately time-wise this summer is perfect for risky trips as I have hardly any commitments. But, as is often the case, when one has the time one doesn't have the money.