We've used Changi as an en route stop twice a year for ages now and have a set routine of:
Buterfly Garden-next to the Ambassador Lounge.
Ambassador Lounge-shower and shave (the wife just has a shower)
Massage parlour (near the kid's playground) for half an hour having the feet done.
Relax-have a beer and watch the world go by.
On the odd occasion we have upgraded to business using our accumalated miles and used SIA's lounge I've kind of missed the normal routine. The lounge is OK but it's so big it's like sitting in a small terminal.