The only disadvantage to a longer veg time is.....it takes longer to finally get to smoke your primo nug
. It's all about finding a good balance between vegging too little with not enough tops, or vegging too long with too many tops. Which definitely CAN happen. I showed my cousin how to top, and he just kept topping and topping and topping his tops and branches, and wound up with hundreds of little skinny stems all over the plant, none of which were big and strong enough to build big huge colas.
You can top for two tops, then top those two and get 4, then top those and get 8, etc. What I usually do, is top the ones that are shooting up the fastest, so that all of my tops wind up nice and even (go back to my pictures from my first post).
But yes, I DEFINITELY recommend combining training techniques. Topping, LST, Scrog, mainlining-- look them all up and see what you want to try out. Something to keep in mind if you are going to top more than once-- each time you cut it, the growth is going to "pause" until the plant recovers, so the more times you top it starts really slowing down veg time. I recommend topping once for 2 tops, and then letting each top get about 4 inches tall a piece, and start tying them down horizontally. The branches will growth straight up from along the two ties down tops and receive hormones that turn them into colas (top buds). It's basically a way to get multiple tops (easily 8-15 depending on how long you veg for, and how well you keep them tied down) without losing all the recovery time for multiple cuts. About 2 weeks before putting them in flower, put a Scrog screen over top of them and BAM!
There are many different ways and techniques, and in time you will find the system that you like best. As long as you have plenty of space, I personally recommend vegging for 2 months from seed your first time or 2, if you can hang in there you will be glad that you held out a little longer for a bigger yield. Maybe later on down the road you could try a bunch of small plants with single tops and little or no veg time. Follow your heart, research your ass off on here, and don't be afraid to ask questions. And remember, less is more with these plants. You don't need to start out trying to pound them with heavy doses of nutrients or anything-- you'll notice that the more you leave them alone, the better they do (as long as your environment is dialed in). The most common newbie mistakes are overwatering, and over feeding. May the force be with you brother.