And even on a small retainer you'd better hope they retained the knowledge of how all that stuff works if you're only calling on them every now and again. This

And even on a small retainer you'd better hope they retained the knowledge of how all that stuff works if you're only calling on them every now and again. This is why we document things at the company I work for. If you're serious about a project and want it to exist for a long time there will be things that only come up every few years, and you won't remember them. You can either write things down or you have to relearn how things work every time. Wroting things down is much easier.