Yeah solvents can be recycled as many times as you want but whenever you use a solvent, various compounds get dissolved and the more you re-use it, the more concentrated they will get. A solvent can only hold so much of a particular solute, so if you use it say 50 times, then its ability to dissolve the waste compounds will be greatly reduced. It all depends on how much non polar waste products are present in the DMT containing plant, and how soluble they are in lighter fluid. So you might be able to re-use it thousands of times with no problem.
Also, there are various ways to clean your solvents. The easiest way is to wash them with an immiscible solvent. You can wash lighter fluid with water, just mix it with warm water, stir/shake, let the two layers settle then discard the water layer. The idea here is that sometimes non polar compounds (the stuff that dissolves in lighter fluid) will often be very slightly soluble in water, so some of them will go into the water layer. For washing polar solvents (i.e. water), theres a trick called "salting out", its where you add salt, and the reduces the solubility of organic solutes, so you can force them out of solution.
If you have a distillation apparatus, then you can keep on recycling your solvents forever.