Never too stressed on arrival to SIN as customs check is efficient. I'm usually in a taxi and home within 40 minutes of landing with no checked luggage, perhaps 45-50 minutes with checked luggage.

If you are worried about lines in Asia, you can always add an APEC card as part of Global Service. I remember the fee being a $20 add on the the existing charges. ASEAN countries will have a designated line that can often times be shorter and I've used it to bypass queues in BKK, NRT, HND, SIN, PVG, PEK, etc. I was rejected in TPE because technically I believe US issued cards don't qualify but YMMV.