I've had a Trek 720 hybrid for the past 8 years or so. I've mostly biked short distances to/from work, but this past year I started stretching my rides out a bit. I did a 100k ride (64 miles) in October on it and struggled mightily. Granted I didn't get in a lot of training time after about 1 month before the ride, but I was still in fairly good shape. It took me over 5 1/2 hours (including 2 rest stops) to complete the ride. It wasn't a race, but I felt like I was one of the last ones in.
This year, I plan to do Cycle North Carolina which crosses the state in a week. Other than buying a nice new bike, which I can't afford right now, what sort of upgrades can I make that will make the ride a little easier? How much difference do tires make? I have 700c x 38 on the bike now. How about gearing? I have mostly the stock components that came with the bike. I also have the upright handlebars with bar end shifters.
If I have a windfall this year, I'll just buy a new bike. I don't want to spend a lot on upgrades for a marginal return. I'll definitely up the training this year too as I think that will make a difference.