it is unlikely to forget it
Unlikely, maybe, but not impossible. Why take the risk? Even if you think your memory is 100% foolproof (it isn't), there are a hundred and one completely unpredictable and unexpected things that can happen to anybody with zero warning which can leave you with memory problems, from a head injury to a bad infection. There's a reason that all good wallets tell you to write down your seed phrase and not to memorize it.
As a backup, I use multisignature backups (2 out of 3) stored on my phone/home pc/work laptop.
A multisignature wallet can certainly be a safe fall back mechanism, but you should still have your seed phrase written down somewhere. I assume you carry your phone and work laptop around at the same time frequently, meaning the chances of them both being involved in an accident or being stolen are not insignificant.
About the memory, I meant if nothing unfortunate happens, like an accident or something worse.
No, I don't carry my work laptop around, it stays always in office. Is kind a desktop-laptop thing.