The OP’s question / concern made me think of this case on a 21 year old client who started treatment November 1, 2012. First session lasted 65 minutes and 752 insertions were accomplished. Most sessions were between 30 and 60 minutes on her upper lip and lower lip. I still see her, but for other areas. Her skin is flawless.
I am comfortable working on the lip flaps for longer than 15 - 20 minutes WITH MY SETUP and strategy. Other may not be and that is perfectly okay! There are many others cases like this one where the same strategy is repeated. When I do any case on any face, I am always watching the skin and I know when to stop and not push it. I have said for years that it is possible to do marathon sessions on the upper lip. The sides can always be cleared, but the middle part of the lip, under the nose, usually cannot be cleared in one session because there is a lot of hair and it is a very sensitive area to work on without anesthetic help.
If an Electrologist is not comfortable working on your upper lip for more than 15 minutes, then that has to be respected! You will still get to your goal one way or another.
The case below was all performed using PicoFlash thermolysis. I still see her for other areas and after three years of observation, her lip is NOT DAMAGED. The skin remains lovely. There are a few hairs that pop through now and then. Five to ten minutes is all that is needed to keep any new hairs under control.
Lip case
Before picture prior to first electrolysis treatment 11-3-12 / bleached hair on upper and lower lip / she had a ton of swirling hair and bleaching may have helped make it less visible, but even so, it was not very attractive.
Close up of bottom lip after several clearances of more than 30 minutes:
After working on the lip an hour:
Before
After
Progression by August 2013 / almost finished/ she is the hairiest young lady I have worked on. Most women do not have this much hair.
Condition of the skin after working one hour:
Marathon sessions are possible…