USAF would have used up much of the airframe lives of these F-16 during gulf wars and Afghan war, so do not expect them to be in long service with Indonesian Airforce. And using canabilized parts does not help to extend the airframe lives of serving F-16. I think these jets will be retired around 10 years after joining Indonesian airforce, unless they fly them sparingly.
We had similar experience with US Marine surplus second-hand A-4 back in 1980s, and they were phased out of service in a few short years. We also canabilised a few A-4 for spare parts.
Fortunately, they're not from gulf and afghan wars. I'm not an aeronautical engineer, so I can't comment on possible extesion of airframe lives of those F16. But I believe Indonesia isn't lack of experts who know about possible airframe lives of those F16 (they have PT DI/Indonesia Aerospace in case you forgot) which give the gov't inputs on this matter. Again, it's a grant, why should they refuse? And Indonesia rightnow is in no position of under a threat of war from a certain country.