I have friends who swear by cashback even if it's 3% simply because they don't value flying premium classes. To them flying is point A to B, the cheapest fare suffices.
Yes, I also have friends who only fly the cheapest fares, so they only redeem for economy, claiming to want to fly to more places instead of premium classes. Now that there is no more fuel surcharge in SQ redemption, economy makes better sense (than before).
For me, it's miles from day 1. I value the scarcity, exclusiveness and experience of premium classes. My 1st premium class redemption was for SQ Suites long haul, and the entire experience totally blown me and my wife away.
Not sure if I'm able to try suites ever (now that the kids need tickets), but we tried the old 1st class the the service was fantastic.
Imagine having to use 2xxk KF miles for the flight which could have cost $20k+, I think it makes perfect sense to utilize high mpd and bonus CC miles.
Enjoy while you can travel without kids. Now that I travel with kids, I spent about 600k miles flying 4 pax to/from US in J. Have also flown with them in Y before, really, J is much easier as they have their own bed, rather than requiring to carry them to sleep.
About S$50k.. I charge my business expenses to high mpd cards as well so easy to hit. Most of my spendings are 4mpd, but when opportunities arise, I utilize bonus signup to get even more miles >8mpd.
You're lucky to get to spend on business expenses. I'd say most here do not have that luxury. My miles also mostly coming from business expenses, but not very constant source and not many qualify for 4mpd (was very good for 4mpd when Samsung Pay citibank promo was active).