Valve motor seems to stall to open. Does this make sense?
If a system is designed to stall the motor while the valve is opened, shouldn't there be something to limit the current to make sure it doesn't go past the stall current?

No. Motors can be designed to operate stalled for a long period of time, essentially continuously. They are sometimes called &quot;torque motors.&quot;

How is this design justified? Isn't the motor going to be consuming the maximum current while keeping the valve open?

The design is justified by saying that 7W is not very much power. The motor probably does not consume more than that when stalled.
There is not necessarily a better way to do this job. There may be products that last longer, but do the job in a similar way using a similar amount of power. It would probably be best to ask local service people if there is a product that lasts longer.
A zone should not need to be heating all of the time except during the coldest night of the year. If it does, it will be unable to maintain the desired temperature some of the time. If there is one zone like that, it may need more radiator or supplemental heating. If all of the zones are like that, th whole system is inadequate.