Is repotting necessary / advantageous if so why?

It's wise to pot up as the plant grows. Less risk of bad watering habits from a plant mismatched to size of pot. Overall health will benefit if you have a well-size pot to the plant and not let it get rootbound. in soil, you also get a nearly full complement of amended nutrients in the substrate. I've yet to see transplant shock in 200+ transplants. I don't doubt it is possible, but clearly a very, very low risk if you do it right. you want the plant drinking down what water is held by the substrate within 3-5 days. A bit longer initially is not a catastrophe, but if it is the norm to stay overly wet for 7-10+ days week after week, you will inevitably grow some nasty stuff in there that won't help your plant. Just as you want to use up any irrigation/fertigation water within a couple days - it can stangate in the soil just the same. Fwiw, if using hand tanks regularly keep my water for 5-6 days before i rinse out / refill. It's not best, but within tolerance. it's also kept dark and in much a cooler space than the grow area, which helps prolong it. A little trial and error and you can learn what is tolerable and what carries risk in this regard and plan accordingly.