DW and I have been in from the inception. My premium went up once when OPM renegotiated with a new carrier but has been stable for the many years since. I chose the Federal program for one simple reason -- OPM oversees the contracts and can help insure that the carrier meets its obligations. While that doesn't guarantee no increases and doesn't guarantee a good result in any individual case it seems a useful safeguard. A case in point may illustrate. The Federal program includes parents (an eldercare feature). When DW and I enrolled we suggested that her parents also enroll and they looked at the program. Wise shoppers that they were, they talked to a broker friend of theirs who suggested that lots of "better deals" could be had by bypassing the useless Federal bureaucrats. Knowing how smart they viewed themselves and not wanting to be blamed for possible future problems if we pushed them into the Fed program, we held our tongues. They signed the dotted line on the broker's suggested plan but then, with literally days to go on the Federal open season, gotchas and extra charges started to show up on their better deal. They freaked out and wanted to switch to the Feds. I ended up spending hours gathering info and filling out their forms and got the application in at the 11th hour. DW's father ended up using his benefits for many months of extra care at a nursing home during the final stages of Alzheimers. DW's mother in law is tapping them now. Neither had any problem getting what was promised.
As always, YMMV.
Every man is, or hopes to be, an Idler. -- Samuel Johnson