Adding more and more things to a spell doesn’t always help it to be more powerful. I have found that that actually can overcomplicate a working and bog it down. The MAX I use is seven, probably five on average.
It also really helps to listen to them and feel the spell out. In my experience it isn’t always the best to work from a strict set of rules. The above just is a guideline I loosely stick to, because things work out the best if I follow my gut and listen to each individual spell.
I thinking of it a bit like cooking. I like chocolate and cinnamon and raspberry and lemon and violet and rootbeer but if you try to put them all together it’s a muddled mess. I like to check in with components and see if they are going in the same direction.