Coinvest programs - do you use them?

Came across another thread here and was surprised how many people were against levering up co-invest - which in other words to me is also against co-investing itself. Hence, wanted to see across a wider audience your approach to your firm's co-invest program:

- Do you co-invest at all?

- If so, do you use leverage (where this is available)?

I had always assumed that among the PE investor path co-investing becomes inevitable and equally a core source of your wealth (second behind Carry of course). Am I that wrong to assume that co-investing and locking up a significant portion of your personal wealth in your own fund is a standard part (and often even a requirement) of the PE investor role?