Kannik
Legend
If this happens, the party effectively has +12.5% chance of success on everything. So all challenges are less challenging; might as well just revise the DC table and remove the spell. Or, if the DM wants to keep the challenge as intended, they can bump all the DCs by 2; once again, might as well just remove the spell as it does nothing except create a lot of extra tabletop chatter and perhaps upset expectations.The party is exploring an old ruin, with traps and such. No monsters, no combat. It is a pure skill crawl and exploration. Is it really a problem if they can cast Guidance any time they fail to try and succeed?
On the whole, choices are good in an RPG for they are what make the game a game and makes it interesting and memorable. When +2.5 all day, every day, on (nearly) everything is possible, it reduces both choices and the challenge (including the potentially interesting results of a failure). Putting limits on a cantrip may be somewhat counter to the idea of most other cantrips, so perhaps guidance needs to be folded into something more akin to a leveled spell like Bless for a more limited and choice-based thing. But keeping it as a cantrip as a straight bonus to skill rolls I say it needs limits to work best for the game and gameplay.