cock ring reducing my stamina? and frequent use?

Hi guys and girls, my partner and I had tried several rings before (we started with a vibrating one which was a massive turn off!) and we've finally found one that's a stiffer plastic fit, we absolutely love it. She's never had a vaginal orgasm before and last night was her first (usually she needs to ride so her clit is stimulated) fantastic! However I find myself struggling to hold back. With regular sex I usually cum when ready and rarely need a break to calm down. With this thing on I can feel myself nearing climax constantly and it's slightly annoying if I honest as we want to enjoy the fun!

coupled with this how safe are these long term? I'm talking frequency of use rather than wanting to wear it for hours! I've always had a hard erection and I don't want to loose that through any damage!

had the same issue regarding stamina with cock rings. Sometimes I could go for ages and on other occasions I had real difficulty holding off (I can usually hold off as long as I like without a ring. I think the wide silicone rings worn behind the balls was the best from this point of view.

Not sure about the issues from frequent use though similar devices are prescribed for ED sufferers so I guess there would be some info out there.

Any tips on delaying? I'm pondering a condom but that sounds dull!

Any girls who have found although their man was just fine before they're now addicted to the ring?

There are some products on here you may find helpful. I've not had experience of them but have a look through the reviews
http://www.lovehoney.co.uk/sex/better-sex-for-him/delay-spray-cream/

And just thought that these might help after reading the reviews.
http://www.lovehoney.co.uk/product.cfm?p=2025