10min looks quite excessive but based on conversations in
https://github.com/bitcoin/bitcoin/commit/7fb7acfc, better safe than
sorry. same for lnd. in any case, 30sec was indeed far too short to
begin with, especially for bitcoind.
services are now stopped in parallel, though. so, the poweroff sequence
goes faster.
16px looks easier to read but IPv6 addresses don't fit in the wifi
settings panel anymore. need to find a better way how to display them or
change font.