There is a point of no return in running older jets. Some maintenance is prescribed by the number of running hours on the jets and some maintenance is by time expired alone.
When an engine rebuild is necessary on a Gulfstream, it is flown to a rebuilder, the engine is removed and a loaner is put in it's place. (after about a week, and all the while a jet owner rep must be present)
The jet can then be flown back home, etc. while the orginal engine is rebuilt.
When the engine is ready, the jet is flown back to the rebuilder and the loaner is replaced with the original. Probably almost a month has passed by then and the bill will be upwards of a million.
Just placing a hush kit (muffler) alone on the older jets is over a 1/4 million$ per engine on a G 2.
A paint job alone will be over $200,000.00. I saw an invoice for carpet replacement and it was $85,000.00 and change.
Course, we could buy all the House Reps a big diesel pusher bus and spend a million each on them................