There is a big question mark regarding why Indonesia does not upgrade their oldest Su-27/30 from the SK and MK standards to at least SKM and MK2 standards. No one has a good explanation.End of service life? Their Su-27s are much younger then the Russian ones. And Russia has upgraded and will continue to operate, Su-27SM variants.
The end of service life rumor might not make sense to you, but the complete version of the rumor sorta makes sense. I don't consider the source to be credible though. But what is true is that Russia did not offer an upgrade program for those first batch. Not after the Su-30 MK2 was delivered, and not as a sweetener for the current Su-35 pitch. And Indonesia didn't push for it either. No high ranking Indonesian official ever said they will push for a Flanker upgrade program.