You have something kind've like this in the Australia system. A bicameral legislature, the lower house is up for grabs every election, but only half of the uppe

You have something kind've like this in the Australia system. A bicameral legislature, the lower house is up for grabs every election, but only half of the upper house is. This means senators are basically elected for two terms, and the turnover is slower in the upper house. There is provision for putting all seats up for grabs in both houses - a 'double dissolution' - which can only be done if parliament is deadlocked. Apart from that, turnover of senators is slower than members of the lower house. It doesn't have the effects you're after though - these senators are still party creatures. I'm not sure I'd like your plan anyway - people change a lot in 29 years, and you would need checks and balances against undue interference. Deep-pocketed lobbyists would only have to focus on one person per year, for example.