I used to run my own MTA, and then I get fed up staying ahead of spammers.
I chose postfix which has a lot of off the shelf support for blacklisting and such, but even so I found that I couldn't stay ahead of spammers and their (new at the time) techniques like reflection attacks.
Anyway, while it's fun to play with this, unless you want to spend time every week keeping it up to date, etc., I found it mostly a drain on other better things I could be doing.
I too ran my own mail server for years. I wasn't as rigorous as you in applying patches.. perhaps monthly or quarterly. At the end of the day though, it was the superiority of the Gmail client that won me back.
I chose postfix which has a lot of off the shelf support for blacklisting and such, but even so I found that I couldn't stay ahead of spammers and their (new at the time) techniques like reflection attacks.
Anyway, while it's fun to play with this, unless you want to spend time every week keeping it up to date, etc., I found it mostly a drain on other better things I could be doing.