Provide longer options for automatically switching off screen

At the moment the options for automatically turning off the screen are 1, 2, 3, 4, 5 and 10 minutes. Due to Bug #1512211 I would like to have some longer options, for example 30 minutes.

I freely admit that my use cases are pretty obscure :-) I would prefer the things discussed in Bug #1512211 to be implemented. But anyway, here goes...

* I'm cooking a meal using a receipe on the web. My hand are dirty and I don't want to manipulate my phone, I just want it sitting there for reference. Irritatingly, just as I need to find out how much salt I'm supposed to add, it switches off.

* I'm trying to get a GPS signal while on a sleeper train, which is awkward because I'm on the top bunk and the only place to put my phone is the table below, and the window isn't a great way to get GPS reception. I expect it'll take about 20 minutes. I want to be able to look down and see my phone, and collect it when and only when it has got a fix.

* I'm debugging a problem on my website and I have a bug report in an IM on my phone. The bug report contains a number of unique identifiers I have to constantly search for. I'd like my phone to just sit there for about 20 minutes while I figure out the problem. Having to nudge my phone every 10 minutes is distracting.