Msg#: 4627076 posted 11:21 pm on Dec 1, 2013 (gmt 0)
URL removal doesn't mean "forget you ever heard of this URL". It just means "remove it from the current index and/or cache". When you do this, the very first thing the search engine does is ask for the URLs to see if they're really gone. If not, they would return to the index in three months. The URL removal instructions actually explain this-- along with, ahem, some more-than-slightly misleading stuff about robots.txt which you can ignore.
Google (specifically)* will go away a lot faster if you return a 410 instead of defaulting to 404. This has to be coded explicitly. But once you've done this, it makes no difference whether the files are physically there or not, because the server never even looks for them. So with 300 pages, especially if you can collapse them into a few patterns, a 410 would also reduce a little bit of load on the server.
* Bing doesn't seem to distinguish between 404 and 410. At least not on my site.
Msg#: 4627076 posted 12:24 am on Dec 2, 2013 (gmt 0)
I have been 410ing pages for 18 months, and Google continues to report them as errors in WMT. They are not linked to from an external source, they were a "calendar error" situation where a page got generated for many years in the future (like year 7632).