Many users here are still having great success with their iPad 2 models running the latest iOS. It is nearly impossible to say with any certainty how long a device will last, especially without know all of the details about how you use it every day. I would start with really basic troubleshooting steps and see if that helps performance.
Here are some basic things to try that might help.
Go to Settings>Safari>Clear History and Website Data
Close all apps. Press the Home button two times quickly. You'll see small previews of your recently used apps. Swipe left to find the app you want to close. Swipe up on the app's preview to close it.
Force restart the device. No data is affected by this. To force restart your device, press and hold both the Sleep/Wake and Home buttons for at least ten seconds, until you see the Apple logo.
Something else that can help is to reset all settings. try this. You will not lose any data, but most of the device settings will have to be entered in the settings app again. Settings>General>Reset>Reset all Settings.
If all of that fails, restore the iOS software. Backup your iPad before you restore, then restore the backup when you are done. If that still doesn't help, restore your iPad as new and start all over again. Most purchased content can be downloaded again at no charge as long as you use the same Apple ID and as long as the content is still available in the store.
Restore iPad to Factory Settings
http://support.apple.com/kb/ht1414
Download Past Purchases
http://support.apple.com/kb/ht2519