Could *you* remember a strong 30-char pw?
Yes - sort of.
Generate a print-out of a lot of entropy. Say a 10 x 10 grid of 5-digit random numbers. Keep it with you. On its own, it can't be used.
What you remember is a hash algorithm for combining the something you have with something you remember to generate a password, that's computable in your head.
For example: Row 8 column 5 reading vertically upwards, six 5-digit numbers. Hash the first by adding d,d,m,y,y of your birthday, each digit modulo 10. The next one, your Mother's birthday. Sister, Spouse, bank sort code (five digits of), bank account # (ditto)
remember: 8, 5, up, self, mum, sister, wife, bank, bank. Not hard.
Better still make the something you have into something(s) with innocent utility. Bank cards. Driving License. Loyalty cards. Torn-off corner of a newspaper stock prices page with a reminder scribbled on it. These don't raise suspicion like a page of explicit random digits does.
Other people will find the surreal imagery trick works better, which is how people have managed to memorize entire telephone directories. Construct a sentence of words that don't normally go together but which do parse correctly. "Green ideas sleep quickly in well-padded spoons". That sort of thing.