If you feel the need to always know what your IP address is then you need a Static IP address, because it is constant. Static IP addresses are more reliable for Voice over Internet Protocol (VOIP), more reliable to host a gaming website or to play X-Box, Play Station, use Virtual Private Network for secure access to files from your company network computer, etc. Static IP addresses are also great if you use your computer as a server, as it should give your file server faster file uploads and downloads. Another plus with Static IP's, when hosting a website you are not sharing your IP with another company who sends out a lot of E-mail SPAM and not only has their website been shut down but in turn gets your IP address blacklisted.
In contrast a static IP address can become a security risk, because the address is always the same. Static IP's are easier to track for data mining companies. Static IP addressing is less cost effective than Dynamic IP Addressing.