hi, i'm new, no experience, i'm buying bitcoin on exchanges

i want to cold store without using hardware wallet.
(i've tried keepkey and it is too complicated for me)

my idea is to use, say a coinbase wallet,
keep 12 words safe & not upload backup to cloud
then transfer all my bitcoins from exchanges to wallet
then delete the wallet

then all i need to do is keep my 12 words safe for many years on metal plate
i tested by opening another different wallet  (bitcoin.com),
then, using these words, all my bitcoins appeared
is this safe to do and still work again in say 10 years