Here is a free way to keep a copy of your Tweets.  You spent a lot of time writing them collectively and there are some good memories attached.  Maybe a friend or family member wants to keep them for the next generation, whatever your reason is there are several choices on how to go about it.  When you search the topic, some of the solutions expect you to be a programmer, some just plain don't work and others are offline when you need them.  Here is one solution that works right now called: TwitterBackup

 

It's a basic Java program so everyone should be able to run it from your desktop simply by downloading it and clicking.  If that does not work for you, you can try fixing your Java plugin by re-installing or just try a different solution.  

Here is the file to download and detailed instructions: http://johannburkard.de/blog/programming/java/backup-twitter-tweets-with-twitterbackup.html

My Notes: you will have to enter a code to enable it to work.  You get that code from Twitter after you authorise the backup program to access your account.  It's fairly easy to do but you should be aware that it's going to ask for the code so do that in a side window.

Keep in mind that you are generating an XML file without styles, which means it's not going to look pretty.  Make sure your file name has the .xml extension.  If you have a spreadsheet program you can open the finished file with that and clean it up which is what I did.  If you are more adventurous you can use a free XML editor from here