If you want to extend your cycle, extend your cycle........with the same compound. Bridging into another liver-unfriendly methyl compound or stack is just foolish.
If all of your health markers appear to be good, and you are feeling fine, buy some more Msten and add another week or two to the cycle. Six (6) weeks of Msten, while pushing the upper limits of safe cycling, is not unheard of. Having said that, 30mg of Msten is a hefty dose so make sure your cycle supports and diet is in check. Anything beyond this is just greedy and asking for trouble. Get your gains and get out. There will always be time for another cycle if your health takes presidence over the gains.