Memorising it would be a nice idea but even as that, you must try as much as possible to still write and keep your Seed phrase In a safe and reliable place till you need them.
If you would still write them down for safekeeping, why then waste your time memorizing them? Manually writing our seed phrases down and carefully keeping them is the best way here and I will not even support memorizing them at all. Though we can try to memorise them in addition to the manual writing, but I can assure you that you might still rely on the ones you write down rather than the ones you put in your head.
We all know how the human brain works, what if we later forget? What if there are mental health challenges and you could remember them again? That is why we should be smart in this regard but also be reasonable in the way we safely keep the written phrases.