How long can urine be kept at 98 degrees/crotch temperature?

First of all I would like to thank every single poster here that has given advice or shared their story and provided an invaluable amount of information to all of us nervous as hell drug testees. My spiel is the same as most, frequent smoker, low metabolism, not enough time to clean up for a drug test which is for a hospital rotation, and scared out of my mind. So I opted to sub using a friend's clean urine in a travel size shampoo bottle. However, due to circumstances beyond my control, I need to keep the pee in my crotch for a minimum of 3 hours (maybe more) with a hand warmer because I also need to allow an hour and a half of travel time by subway from my friend's to the hospital that is doing the drug test and I need to fill out an absurd amount of paperwork at the hospital and also wait for other applicants.

Therefore, my question to anyone that's willing to answer it is: will the urine be fine at 98 degrees for 3+ hours? I've searched the forums here and google and I've only found the 8 hour room temperature fact. I understand that the integrity of it could start to break down at a temperature higher than room temperature and I'm scared as hell that it would invalidate the test result and I am very uncomfortable using synthetic. I'm not sure if the test will be EMIT or GC/MS but I know it is not an instant strip test because it takes at least 24 hours to get the results. Thanks to anyone that's read so far, any guidance is greatly appreciated!

Also, here're my stats:
Male, 5' 10'', 205 lbs (definitely overweight), low metabolism, smoked 1-3 bowls (vape/bong) a day for a year, stopped for first 3 weeks of May, and continued after that with sometimes as much as 5 bowls a day until 13 days ago when I found out about my drug test and stopped. The day of the drug test (this coming Monday!) I will be 16 days clean. When I stopped smoking in May I tested myself with my first void of the day at 2 weeks clean and failed miserably. I also tested myself today with the second void of the day after 2 weeks clean and failed as well =(.

with two pars of boxer briefs on(bottle in pouch area of first pair) and a pair of blue jeans my quickfix stay roughly 97 degree according to the digital meters and it says 94 on the bottle for as long as i have the bottle in my pants. Drug testing labs use the same thing as a home test except in case of a positive result then they'll use the good test to confirm. pratise makes perfect, you got today and the weekend which is plenty of time

Thanks a lot for the reply biggmoneyme, it really does help calm down the nerves a bit! I've been practicing this entire week with 2 pairs of boxer briefs and a hand warmer and the hottest the practice water has gotten is 102 degrees, which should be fine considering it drops a few degrees when pouring it into the test cup. I'm just worried about the consistency and integrity of the human urine that I'm getting from my buddy on the actual test day because it will be in a non-sterile container for 3+ hours at 98 degrees. I'm worried that either the heat or bacteria or both would somehow mess with the pee and invalidate the drug test.

i really think the temp strips are a couple degrees off, considering it does have to measure through plastic. i went for a UA monday and i used my real urine and when i pee'd into the cup i think i want to say it was either 94 or 96 according to the cup

Well, hopefully the temperature won't be a problem then. I just have to practice opening/closing the bottle silently and stealthily stashing it back into my undies. I have heard from others that at this hospital a nurse stands outside the door while you pee but do they really listen for that kinda stuff?

subbing piss is probably one of the easiest things you'll ever do mate

That legitimately makes me feel so much better man. I've got everything riding on passing this as does everyone else in our situation so thank god there are people like you to keep us from losing our minds! I appreciate it wholeheartedly!