I guess the old type (round brass) Wirsbo manifold valves might have a MTBF around 25 years ?

Never had an issue with the valves themselves since installed 2001 (the Motorized Valve Actuators were another story). Two (of 7) valves have give up on existing this year.

One was stuck closed , I verified the actuator was working. So I removed actuator and lightly hammered on the valve drive pin. It opened, but now it's stuck open (probably ripped the seal). The other is stuck open (maybe ripped upon first actuation this year ?).

Already had delayed the full replacement of boiler and piping for a couple of years.. I guess this summer will be the upgrade.

Trying to balance the heat into those two rooms (master bdrm and laundry) using just the throttling valves on the supply manifold. Kinda working, will take some playing.