The Russian Parliament, the Duma, is a rubber stamp legislature. Putin will be in power until he is unable to control the system.
Here is a translation of a Russian article https://snob.ru/selected/entry/132213
The contrast with Soviet times is instruction, Krasheninnikov says. The USSR fell apart when the CPSU ceased to be a constitutionally defined power vertical. The soviets were simply “a fiction,” with real power in the party and its nomenklatura control. “This was the true power vertical in the USSR.”
And it was far more important in ensuring stability and the transfer of power than the loyalty of the security agencies or anything else because everyone looked to the party hierarchy with the Politburo at the top and knew that it could and would take decisions and then impose them on the country.
“Now,” the analyst continues, “the situation is much more unstable. With the exception of the president, all those organs of power which run the country according to the Constitution are de facto fictions.” The most important decisions are taken by the president and an informal grouping of people around him that is nowhere defined by law and the constitution.
Consequently, in the Putin system, “there is no single ‘party of power’ or even more a Politburo known to all. Instead, there is an indefinite circle of trusted people who are close that is formed exclusively on the principles of long-standing friendship, common fate, family ties, similarities and other informal characteristics, among which chance plays a key role.”
http://windowoneurasia2.blogspot.se/2017/12/putin-regime-less-stable-than-soviet.html