Originally Posted by pvaudio
The longer you put in on the court, the more you put your body through. As I'm sure you're well aware, you need to give your body a chance to recover if you want to get better. If you're constantly building muscle and increasing flexibility, going hard 4 hours a day, every day for a year is not maximizing what your body can give you. You're going to need an off day or two, and even then, all that time should not be spent playing tennis.
It sounds awesome and good on you what you're trying to do - I for one am certainly jealous.
Perhaps you already have a holistic plan in place or you're figuring it out as you go, but I do hope you're incorporating fitness, coaching, proper nutrition and perhaps a little massage here and there into your regimen.
Back to strings:
Alternatively, find a local High School kid that knows how to string to get your racquets done at a good price?
If you get a little bit of a ranking, you could always apply for sponsorship with a string company - I'm a pretty crappy player but I do enjoy a partial sponsorship from a string company with decent poly products - it helps.
Or you could always open a stringing business and get strings at wholesale prices.