I think it would be hard to say either way, at least for Brezhnev. Brezhnev didn't really 'need' to be held in check because his style of rule was more about accomodation and consensus, with a lot of decision making tasked to other figures in the Politburo. But there aren't any clear signs that Brezhnev did this because someone was twisting his arm or that he felt trapped. Even the supposed 'conflict' between Brezhnev and the more economically reformist Kosygin didn't actually occur at a high level - it was resolved lower down the chain (and possibly without Brezhnev's direction) and Kosygin was never outright shutdown in the way Khrushchev's opponents were. The same approach is also apparent in general policy - for example the policy on consumer goods was a bit of a compromise between the party-state and the general population.

So for example the policy and decision making in the lead up to the invasion of Afghanistan didn't involve Brezhnev - instead it was sorted out by 2-3 Politburo members out of session and they reported their findings (see Roderic Braithewaite's Afghansty). Another example of delegation is demonstrated in Benjamin Peter's recent book How Not to Network a Nation - a somewhat important meeting to decide the future of the OGAS project occurred without Brezhnev or Kosygin being present. The former being in Azerbaijan at the time and Kosygin being at Nasser's funeral. Instead the meeting was chaired by Mikhail Suslov and a decision was reached - and wasn't subsequently challenged. The description of those prescendings also tend to suggest that while there was disagreement, it wasn't an overt power clash and in the end (contrary to Peters' analysis) the final decision was about practicality rather than power blocs.