I've ridden many 100 milers and many over that distance in a day. Some back to back, others were "fun rides". And I've never owned a power meter or power tap yet I was on par with a male co-worker who was younger and used powertap for his training.

If you want to absolutely hit your maximum performance, then it might be worth it. But personally, I would have to agree with Emily. Start riding a terrain (up and down the hills) that is similar to the tour ride. At our age, ahem I'm up there too..., rest day is extremely important! When young you could over do it and bounce back in a day or two but when we get older, we just don't bounce back so quick. o listen carefully to your body. There are days when you just don't want to ride. It's okay to break from a training schedule. Your body may be telling you that it needs a break.

One thing people forget is your diet. Eat a really healthy balanced diet. I still don't drink typical carbonated drink e.g. CocaCola, instead drink OJ, fruit juice, lots of plain WATER. OKay so I'll admit I drink too much Chai Latte and home made ginger beer naturally carbonated with plain old sugar.

suggest you look into some high end sport drink NO GATORADE and the like but a real sport drink or mix. Don't expect to lose weight though...

Yesterday's menu:
brekkie: miso soup with tofu and scallion; chai latte
Lunch: vegetable stir fry; tea
din din: braised burdock root with carrots with bit of meat (gobo kinpira). lots of water

Drank lots of water and unsweetened tea.