Wiping the scores on a single leader board is a huge mistake in my opinion.
Some people play games just to compete with scores on leader boards and investing the time to get to the first position, only to have it erased is a definite turn off.
Sure, saving your all time high is good, but if others do not see it then it doesn't really have the same significance as opposed to having the world see it on a leader board.
Some golden age arcade games have world records that were set in the early 1980's that still have not been beaten.
Of course, those scores were recorded manually by arcade owners, then validated by Twin Galaxies, but the TG database today is up to date and includes the old scores.
Sure, this is not a golden age arcade game , just a casual game for smart phones, but the competitiveness of leader boards is the same.
My suggestion is this.... have more than one leader board, like some modern casino sites and other popular games do.
So, there is ....
1) An all-time-high leader board (100 or how ever many slots you want but at least 50+ is recommended) .
2) Monthly leader board
3) Weekly
4) Daily
You could get that down to just two if you want, like an all time high and a weekly for simplicity.
Multiple boards would not only give someone a chance to compete with the insane all time highs, but new comers to the game would also have a chance of at least getting their score on a leader board that is refreshed.
That way, you could appeal to casual players who like to compete, as well as the serious players who want to maintain an all time high position for a legacy score.
Sure, that assumes the game will have people playing in months or years to come, but simple games that are addictive can grow into something big over time (like angry birds), so you never know.
This doesn't really matter though if your leader boards are not going to include 'handle' (user names), and I do not see the point of a leader board without one because a player cannot prove to their friends that the score was actually their score.
With that said... I also recommend including the player names (even if only 3 initials) to your leader boards.
EDIT
Thanks again for this thread.
Talking about the leader boards made me go and check my world records, which I have not checked in over a year, and I found that my 21 world records are now down to only 16. (this will not do)
Looks like I have my work cut out for me to reclaim my position on some game titles, especially my favorite that I used to have 3 records on separate tracks for that game title.
At least I got beaten out by a celebrity world class gamer John P McAllister (Redelf) who has 153 world records, so definitely not a scrub, but getting knocked to 2nd place still hurts.
That track (leader board for specific rule set) has only eight scores with the oldest being set in 2015 when it began, because the first high scores were so high and usually people only submit a score that can beat the existing 1st place rather than submitting scores for adjudication that are not world records, but some people submit scores for 2nd 3rd etc on other tracks, just depends on the game and the player. (Donkey Kong tracks get lots of less than first place submissions)
Anyway, in the world of competitive gaming, wiping a leader board is about as popular as crucifying Jesus.
Coding things my way since 1981 -- Currently using AppGameKit V2 Tier 1