do you take them at the first symptoms or wait until you really feel you need them?
Do we know if treating the symptoms has any effect on the course of disease and its prognosis?
Do you mean UTI (urinary tract infection)?
If so, I went through about an 8-month period where I had recurring UTIs. After the first one, I started taking either Azo or Cystex at the first symptoms (pain, for me). I think in maybe one instance the OTC stuff seemed to keep it from progressing to a full-blown UTI, but after several cycles with an antibiotic and recurrences, I finally got a high-powered antibiotic that knocked it out for good.
Anecdote does not equal data, and that looks like what your 2nd question is after. Can’t help there.
If you really did mean URI, not UTI, then pardon my TMI and carry on. 
I think you mean UTI (urinary track infection). Taking Over-The-Counter medications for Uniform-Resource-Identifiers (internet addresses) is contraindicated. You can get loopy and start accessing porn sites or Rush Limbaugh and Ann Coulter sites.
Sorry, I was thinking Upper respiratory tract infection - Wikipedia, the free encyclopedia Wikipedia uses “(URI or URTI)”, I don’t remember ever seeing the latter before. I will ask mods to change. Who knows it might work.
Title clarified.
— Ellen
I rarely take anything OTC for a cold, and they don’t have any effect on the overall course anyway. Though I could imagine that using a decongestant might reduce the likelihood of something progressing into a full-on sinus infection (if the nasal passages are super-swollen, sealing things off and letting bacteria brew).
Of course, as I understand it, a full-blown bacterial sinus infection isn’t all that common, most are truly viral, but I could be misremembering.
I usually try to wait until I’m practically on Death’s doorstep before I take OTC meds for anything. As it is, I have 11 pills of various types that I must take every day for my coronary artery disease, and wish to resist adding to those for as long as possible.
I start taking medicine when I get uncomfortable–when it gets hard to breathe, when it gets hard to sleep, when I cough enough to get tired or not be able to sleep.
I’m prone to sinus infections and I feel 100% sure that taking decongestants helps to head them off.