We need something. I agree with limiting lobbying. Maybe even have non-compete type agreements where a politician can't work for any lobbying company for two years post-service.
I do think if politicians had limited terms, many of them would end up being advisors to their replacements, and I still think they knowledge base would be there.
The bedrock of this amazing country was based on the ideas of 30-40 year olds. I think fresh blood would be good. Orrin Hatch is a good example. Started out as a good politician, but eventually lost touch with what matters. Dude wears full on makeup all day every day. I don't want "professional" politicians. I want people that just want to serve. The different mindset would make a huge difference IMO.
Could senior staffers have more influence? Sure, but they won't be the ultimate decision maker. A politician with one long-term stint won't have to bow to lobbyists or special interest groups. They can do what is needed to better the country.