NO NO NO save them for the next lucky board event, the key consumption is NOT worth it, in lucky board you actually get rare ninja fragments and other free stuff and by spending like 500-1000 coupons you can actually get lots of seal scrolls too usually enough for a 10x pull.

if you really want you can save like 990 coupons and buy a ''key pack'' that has 88 keys and usually it comes with a 20-30% discount so you can get it for cheaper, wait for that event.

trust me I had over 1k coupons and 1200 ingots and I went for sage jiraiya and jigukudo frags (I needed 40 frags of each) instead of keys.