My ideas for longevity
1-Use a replaceable SD card for swap save your internal MMC
2-keep backup images and backup of repos
3-DO NOT use the double-Scud battery hack, this flexes the system board and has caused me 3 no-Sim N900s, not sure if it was the battery or cover causing more flexing
4-charge your phone in a drawr where the phone is not at risk of falling
or bending the USB port
5-a screen cover and case are a good idea, though I have a good number of spare screens and plastic at this point
6-use a bluetooth headset, better to keep your N900 in a safe dry pocket than risk leaving it somewhere, a Pebble smartwatch even lets you skip songs and preview SMSs

at one point I was a big believer in plugging the USB port with a Qi stick on charger but it turned out to be a big bother.

I seriously cant believe that in an indeterminate time I will be either stuck making a crappy rPi phone or dreaming for the apparently permanently delayed(fusion power and flying cars anyone?) merging to mainline kernel for android giving us access to those crappy but at least usable(like in Maemo)bin drivers for the kernel versions they are released for.

I have a up to date Android tablet, the hardware is fine, the OS is crap, but I like having Gnu tools to work with and being able to have several live windows running. I know how to close programs when I am done with them.