Will the Simonton 5500 windows last about 30 years?
The windows aren't going to fall apart, but 30 years is a long time for vinyl in Texas. The windows will still be functional, but they may not lock easily, open and close smoothly and will probably be leaking more and more air as the years go by. This is just my opinion though, and some will disagree with me. If I knew I was going to be in the house for 30 years, I'd at least consider thermally-broken aluminum windows, as they will hold up much better.
If you decide to go with the Simonton 5500, I'd highly recommend getting the optional
reinforcement for the sashes, to help prevent bowing/warping.
You've listed (4) 64 x 60 sliders, and (1) 40 x 70 double hung, and I would just say that these larger windows are the weak links in the job. The larger the vinyl window, the more likely you are to have issues with bowing over time.
I try to avoid commenting on price, unless it's outrageously high or low, since I haven't seen the job and don't know what all is involved. In the end, all that matters is whether or not you feel it's a fair amount to pay for the work offered.