Hi Mark
7 hours is definately too long to dry.
I have not seen the Texatherm in action but i use Dry Fusion which i find works very well on carpet tiles regardless of condition ie spillages etc, especially synthetic types. Normally dry in thirty minutes.
If I was going to hot water extract, I would normally use either solutions, or an enzyme product as Glyn said like Fastbreak.
But the main requirement would be plenty of agitation and dwell time, then extract with either water or an acid rinse. Followed by a bonnet to extract surface dirt and extra drying.
It would'nt matter if I used the truckmount or the portable the drying time should be roughly about the same, the truckmount would be quicker because of the heat and power etc. I would be looking for 2-4 hours drying.
Derek Walker.