Also your argument is along the lines of thinking I argue for: You say I shouldn't lobby for regulation I believe is beneficial because a future government might change the regulations to make them not beneficial. This implicitly assumes that the future government wouldn't implement the non-beneficial regulations if the current government doesn't do the beneficial ones. Possibly! But this is arguing that we should firmly establish principles, values and precedents that future administrations will feel bound by. And that I would agree with: Regulations and governance should arise from principles (practical details and grey areas will always require a ton of messy detailed negotiations, but within the confines of principles!). One of the things the current US administration has done is to show that it is possible to disregard principles if you are powerful with no consequences. You can lie about elections being fraudulent, watch your supporters storm parliament and get reelected a few years later.

But if principles don't matter to those in power then the conclusion is actually the opposite of what you say. While your allies are in power you should use power however you can to further your interests, because when others are in power they will not feel bound by your restraint, and at least they first have to undo your work.