Login sessions on iOS time out brutally fast

[Gabeg]

I switched servers at my ISP from GoDaddy to Roundcube Webmail 1.3.8 -- mostly fine but very annoying rapid session timeout when using any browser (Firefox, Safari, Chrome) on iOS (iPad/iPhone). There's no timeout using Windows browsers and there wasn't timeout using GoDaddy server. I don't see any iOS settings to control this; it's puzzling why Roundcube doesn't like these devices!