Michael Daly wrote:

303 Protectant ... on inside ... will prolong latex by a factor of 3-5x.

My experience is the opposite ...

Could be the latex in your jacket was of higher quality, or newer.
Perhaps this 303 business is an urban-stream legend. But probably not,
given all the equipment vendors recommending its use, for example:
http://www.kayakacademy.com/gasket.html

If you have cuffs and a collar over the latex, you don't need much
UV protection compared to the suits with exposed latex. I'd say use
the 303 sparingly on the latter and not at all on the former. I'm not
convinced that 303 doesn't cause premature deterioration of latex.

The benefit of 303 on latex seems mostly for lubrication, rather than
UV protection. Some latex lubricant might work just as well or better.

FWIW, I've never heard of perspiration damaging latex.

"In general, Latex will decay from salt/sweat."
http://www.purplepassion.com/purple-passion-hints.html

OTOH, "Saline will not ... deteriorate the latex."
http://www.cervcap.com/faqs.html