At what point is a MYSQL database considered to be too large to the point where it seriously slow performence? My database has currently 150 tables, 12,000 rows and 43MB of data. And the number grows by about 15 rows (60Kb) per day 5 days a week. Should I be looking at alternate ways to store and retrieve my data? or am I fine for the next few years.

You are not in danger of running into problems with the size of your database. There are companies running MySQL databases with billions of rows. Check out some user stories at http://www.mysql.com/press/user_stories/index.html

Thanks