I like to experiment and change things often. And for the 3th time in a few months I will be completely changing my website. That means the third time all pages will result in 404. I don't really care about serps (that website don't receive a lot of visitors anyway) but I'm concerned about some kind of permanent penalty. It would be stupid to penalize for something like that (after all things happen, website/owners change) Google shouldn't give any permanent ban for that, but with them you just never know... So what do you think? Any evidence of long-lasting effect of changes like that.
Na I carnt see them ever banning you for it, as you say SERPs and site traffic will be effected but you can always put redirects in place and make a custom 404 page with site search funtion/sitemap or navigations system in to help your visitors.
I encountered before, just when I changed my blogs (blogspot) title, I suddenly lost 90% of organic traffic maybe due to possible duplicate that Google algorithm considered having the same content but with different title for a single blog but I'm sure Google already overcome this kind of problem. I just give few more updates and strong backlinks and a month later, everything slowly returning back to normal..