Hi Telomi, I just joined this forum and am also in possibly pursuit of a health career although may not be the same as yours nor completely known yet. (Just a disclaimer for my 1 post count).
However, posts like Matthew9ThirthyFive are extremely rare and unrealistic. Although it is doable in some cases or others, the question you really have to ask yourself is how well will you come out on the other end with an "A" or a passing grade or whatever you will need? Working 70-80 hours a week and taking four courses every term is not realistic in many cases and this would be a RARE statistic to come out doing well on the first try for those classes with that kind of workload. If indeed Matthew9ThirtyFive accomplished this, kudos to him. He is a part of the rare accomplished statistic but to anyone else that is looking to build their way up, this type of response isn't for them.
From my experience on fighting into to get into tough programs etc (although not medical related) EVERY "A" counts. especially if you need to build your GPA up to get into a program or become more competitive on your applications. Working a full time job (40+ hours give or take) and doing these pre-req science classes full time are going to be difficult. They will be time consuming on their own and to do well in them to come out with an A will require a lot of dedication and work.
You'd really need to ask yourself ( as I do to myself) to know how much you can handle at a time to pull out with a good A rather than to speed up the timeline on completing your pre-reqs regardless of how bad you want to get it done quick. This would definitely be rushing. Once you apply to med school, your chances with the good grades on your pre reqs from the overall GPA and your MCAT score when you apply be also be a big determinant to my knowledge.
So while doable, how well and competitive will you be rounded out to be coming out at the other end is a good question to pose