My doc lets me do that so I can nip an outbreak in the bud, so to speak. The antivirals have a very long and excellent safety record, so there's no problem in that respect.
There's no medical/scientific basis at all for urine helping anything like herpes.
It's really a situation where your immune system is what normally keeps the virus suppressed. If the immune system is being challenged by anything from a health issue to emotional stress, it can allow an OB to get started. The sooner you start the meds, when you feel one coming on the better. Given your recent history of frequent OBs, a doctor should give you a suppressive script. If insurance and cost of meds is a problem, get generic acyclovir, it's much, much less expensive than Valtrex or Famvir and it just as effective for most people. The down-side is that you have to take it a little more often.