You have been given a load of bollocks by someone!!
The heat sheild though a good idea is not totally needed, mine has none fitted.
Reglators are combined with rectifiers on this car and it is most likely to be the rectifier not the regulator at fault, although if either is faulty the end result is the same ie no charge.
They are very reliable devices and if you are going through this many, either the place doing them is crap as they are easy to do or you have a MAJOR IMTERMITTANT SHORT CIRCUIT SOMEWHERE.
I would inspect all the main battery leads for shorting, at the battery tray as well.
A battery does not just go flat, it stores so much energy, the heat needed to flatten would give a lot of tell tale signs.
What else happens, does your warning light come on ?, does all trrace of battery power suddenly go.
You may have a break in the main wire feed(live) near battery they corrode very badly on cars, what is the voltage when charging ?
Have you got stack loads of ICE ?
More specific info needed.
tabetha