Interesting...... in 2023 only 8 "amateurs" broke 3 for men in SG (these include ex SEA games fellas or TEAM Singapore / subset Singapore Athletics)....discounting those local record holders like SRY or Benjamin Khoo who probably have very good genetics and excellent background etc.
For 2023/2024, no women broke 3 in SG. A few came very close tho.
edit - basically same story for 2022
Or if we take 2:45 overseas as the standard in which you pretty much can be confident that you have a very good shot in breaking 3 locally.
Edit - not a pro, i just eyepower some PB examples, it might even be closer to 20 mins / 2:40 overseas
So breaking 3 in SG for hobbyists like us with no serious background other than just following some plans and having good consistency seems like it's quite the barrier / bragging rights in the local context where you need to juggle family and career or at least your sian day job.
And when some might finally be able to retire early and have loads of time to pursue these endurance hobbies (eg lets just take age 55), it's nearly impossible by then.

Or if you age 40 kena Toto grp 1 then power lah dey.
And of coz, if you are just basing it off 1 single certified race per year ie SCSM , then lagi forget it...... by sheer probability alone you are already down that much. Anything screw up like it rains or nutritional absorption screw up or wanna cramp but it's still not full blown type, it's bye bye unless you have trained much and have lots of buffer.