So what would it take to keep the same plant growing, flowering, budding? Personally, I'd much rather not chopping down plants and killing them to harvest.
There is a process called revegging, which basically means that when you harvest your plant, you leave a small amount of growth on there and put it back under a veg schedule for a while.
The downside iis that revegging takes a while, initial growth will be mutated, and you weaken the plant's genetics considerably by doing this, which may make the plant hermie.
On the upside, the mutations caused by revegging can make for some cool looking bushy plants, particularly if you leave a small amount of bud on there as well.
I wouldn't recommend revegging though, for the reasons I gave above. If you want a true perpetual system, you simply need to set up seperate veg and flower areas, so there are always plants vegging, ready to replace plants that get harvested. You can do this with as little as 2 plants (one in veg and one in flower at all times), or lots of plants, with harvests every week in a staggered perpetual grow.