There is IMHO no real "too fast" or "too slow", even though excessive speed or the lack thereof creates some problems.

What's more relevant is IMO a healthy speed/revs ratio - a "good" benchmark is a 1:1 match of speed and hand revs, so that there is enough revolution on the ball to make it react in the time it has as it goes down the lane.

But: Low speed (I'd say 10mph or less) creates roll-out issues with weak hits and lack of drive through the pins, while high speed (hard to tell the limit here, but I'd say anything 20mph and beyond is contraproductive) increases the risk of pin "splattering", just as if you play with a polyester piece. The pins do not stay low and mix well, or the ball simply passes too quickly through the deck to mix it up (so wide-open spares and splits are frequent). I have seen some players in my league who tzreid to compensate for their poor release with brute force and speed (with matte particle balls even on light shots balls) - while some hits created impressive and loud strikes, most of the time you could count on those wide-open leaves and poor spare game on single pins to ruin a potentially good game. Such players hardly appear in higher leagues around here, only in house leagues or the lower officual league ranks, because they either only play "well" on their familiar THS or are too erratic in results to be a valuable player for higher leagues where competition is pretty hard and tight.
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The thing I would be concerned about is whether or not you are doing these speeds with muscle or gravity. As long as you have a nice free swing and can keep the speed the same, there is no problem. If you muscle it to get there, then some adjustments need to be looked into.

i thnk if u have enough revs to make the ball face the pocket the correct way, then u r good
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When a house bowler misses the mark, misses the break point and strike, for many ppl its called a wallshot. When a pro does that its call adjustment

When a house bowler gets his finger stuck in the ball and fall on the lanes, for many ppl its called lame bowler. When a pro does that its called the Machuga flop! ha i like this one.