I've been struggling trying to balance my radiators.
I noticed in SEVERAL unimportant rooms (utilty, toilet, etc) that the
rads get very hot even with the LSV down to 0.5 turn open AND the TRV
set to snowflake.

Seems like bad TRVs, so I bought one new one as a trial and confirmed
this (now fixed in that room).

A bit of Googling revealed someone stating TRVs have a limited life,
eg 5-7 years. These might be 15 years !
So that appears to be true.

If I'm going to swap ~10 of these, then it's not cheap, as I just paid
£15 for one LT117E
Also they don't sell the head only.
Out of interest, what is the fail mechanism ?
I guess no chance of fixing ?

Thanks in advance.