The effects will not keep getting stronger, they don't stack up because you get tolerance and the doses are quite low to begin with. The first "attack" dose is always important, and to re-up the trip you generally need a little more each time.
But at 30 ug it's possible you can just keep extending those threshold effects. At that dose range it may be different. But my experience with LSD is that if you try to extend the trip, it just feels generally blissful and transparent, but not so psychedelic / chaotic. Unless perhaps you try to go to sleep before the effects are finished: that can produce some wacky visual noise / hypnogogic hallucinations.
For me the best anti-depressant action and help with focus in my life come from the really noticeable trip effects of a decent dose anyway, because that is when you are confronted, taught lessons, get really deep insight. But I have managed a very therapeutic trip with about 60 ug or so.
Not sure if you can compare it with your potency, because mine was generally lab tested in the past while what is "said to be" the potency by dealers in general tends to come back as lower result from the lab. Most of the time I'd say, in my experience.
If you think it's important to check on info of low-dosing only, here is the centralized low dose thread:
http://www.bluelight.ru/vb/showthread.php?t=266623
