Can I install thermostatic radiator valves on a hydronic heating system?
Excess pressure?

No.  Residential circulating pumps can only produce limited head pressure.
Early pump failure?

No.  Life expectancy of residential circulating pumps is not usually affected by changes in flow.
Other concerns?

Maybe, depending on your exact layout.  Response time of wax motor thermostatic radiator valves is slow (20+ minutes) and restricted flow through partly open valves may distribute heat unpredictably where there are multiple radiators in series in a single branch (or ladder rung).  From the Taco "Hydronic Zoning Seminar - Residential and Light Commercial Applications":



  Series Loop Zoning
  
  While thermostatic valves can be used in a multi-zone series loop
  system, electric zone valves or circulators are a better choice for
  series loop zoning.  The reason:  the modulating characteristic of
  thermostatic valve operation can result in unbalanced heating within
  each zone.
  
  If thermostatic valves must be used for series loop system zoning, it
  may be necessary to balance radiation by adjusting baseboard dampers,
  or by removing radiation fins in a room that is overheating.  An
  outdoor reset control may also be required.


Also, depending on the type of boiler you have, it may have a minimum flow and heat delivery requirement.  Too few thermostatic valves open within a zone may cause the boiler to not work well.