Flexwatt and Thermostat Question

So I've read in a couple of threads here now that you shouldn't let flexwatt get over 100 degrees. I understand that it could shorten the lifespan but other than that, why? According the manufacturers website, 11" Flexwatt can reach and maintain up to 150 degrees safely. So why would 100 degrees be bad?

I mean if you have non-proportionals like I do, the flexwatt will exceed 100 degrees easy to get the temps needed in the tubs. I know I am not alone here. I know a few that have had their racks setup like this for years with no issue.

Even on my proportional, the temp exceeds 100 degrees to get a 90 degree temp.

The tubs are in no danger of melting. I'd had to exceed 225 F to get that to happen.

So other than potential life expectancy, what's the big deal?

Thanks.

No other reason, just the one.

Mine is set to 104.