yes you are all right, @OT, @runningbitcoin, @bitalion so scanning has a few mechanisms to save time and resources, it definitely starts at an arbitrary point in time, the cake node for example only scan blocks from the first day of this year on, since there were no known implementations of receiving SP the years before, (even though there was one in development for bitcoin-core) and another thing is as time passes and more blocks come in, that also means more old taproot outputs end up being spent, so those taproot outputs can be skipped as you don't need to scan a payment that is already spent by someone else, therefore by scanning only unspent taproot outputs you find faster which ones you definitely received and did not spend yet, so older blocks end up scanning faster than newer blocks.

So the time to scan will always depend on the size of the scannable taproot output utxo set, and also depends on the device, but recently I was able to scan all blocks on my phone (samsung phone) on cake wallet in under an hour, which was about 37k blocks.

But also you don't need to scan everything all the time, you can start scanning by a certain date, or stop scanning when you've found all payments, etc