You can keep your current class as long as you want, as long as it suites your needs. But when you do upgrade, I recommend you test for General and Extra during the same test session. It's a lot easier than you might think. Practice exams, that contain questions from the actual exams, can be had on
QRZ.com. Once you are scoring 85-90% regularly, your ready for the tests. Extra doesn't give you a lot of privileges over General, except to say you did it.
I think they throw a parade and give out free ice cream, if you go all the way to Extra these days.
NOT!
I stayed a Novice for a very long time because, I only worked CW and that had plenty of band space for me. In the early 80's I lived in Germany and my US Novice made me eligible for a German Class A license. But, in early 1999, I went from Novice to Extra in just 3 months. I took the Technician, General, and 13 WPM Morse tests in one sitting. Then, 3 months later, took the Advanced, Extra, and 20 WPM Morse test in a second sitting. As long as you are prepared, it's easy to do. I could have done all of the tests in one sitting, except for the Morse tests. However, you don't have to deal with the Morse tests any more. It's just two tests to reach Extra.
I did do some 2 Meter AM (Heathkit Twoer) work around 1965-66, but that was before repeaters and FM got popular. Back then, I only had one crystal that put me directly on 146.000 MHz.
It's probably not a good idea to do that today.