Keep all spam in the Spam folder?

I currently have 45,886 spam emails in the Spam mailbox. Do I need to keep them all in the Spam mailbox?
BTW, ever since I have updated SpamSieve to 2.9.47 every time I “Train as Spam” I have to wait 15 or 20 seconds before I can do anything else with my email. Is that because I have so many spam emails in the Spam mailbox?

I realize that I am replying to myself, but I just wanted to add this, since it pertains to my question:
I just noticed that the emails I train for spam are NOT moving into the “Spam” folder anymore, since the 2.9.47 update, they are now moving into the “Junk” folder.

It’s up to you. SpamSieve doesn’t need them, although it’s good to check for any that are actually good before you delete them.

Probably not, unless you had enabled debug logging. You could record some sample logs from Mail and the SpamSieve app to investigate the source of the delay.

We changed the default from Spam to Junk a few versions ago, although nothing should have changed for Macs that already had SpamSieve installed and were using Spam. You can use the Change Settings command to control which mailbox is used.