Too late ...

Only one plate was broken, so only used one new plate. Advice for anyone doing this. Have a vise or wide-mouth Vise-Grip to compress the plate/rivets.

Checked chain stretch with gauge and drivetrain wear. All Good to VG. To be expected (in spite of millage or age) given my non-aggressive habits and regular clean/lube maint.

Tested on my usual 10-mile every-other-day trip. Normal shifting, gentle riding. (I've NEVER been an aggressive cyclist, nor do I do anything other than city/commuting.) All smooth, and link secure upon check after ride.

Any bets on how long it'll last?

I did end up ordering the KMC X8.99 and will keep it in the pannier ;-) But I'll hold off installing until the SRAM gauges bad (stretch) or breaks another plate.

BTW: It's on this machine ... a much-modified Gary Fisher 20.5" 'Advance' mtb frame (late 1993). It's my grocery getter/commuter with probably over 20k miles....