Do older models always lag behind/run slow?

Question

The reason why I ask is I currently have an iPhone 4S. I got it in July of 2012 right before the iPhone 5 came out. After iOS 7 came out I noticed performance decreases. I don't think I had any major performance issues before 7.
My question is, do older models of Apple products lag behind when they release updates? I want to buy the new iPad mini and want to keep and use it for years to come(more than 2) but I am concerned if it will start showing performance issues when Apple starts releasing updates.
How good is an Apple product before someone has to upgrade? Do the older models lag badly or is this just an IOS 7 issue..

Answer 1

If You Think iOS 7 Feels Slow Here’s How to Speed It Up
http://osxdaily.com/2013/09/23/ios-7-slow-speed-it-up/http://osxdaily.com/2013/09/23/ios-7-slow-speed-it-up/
You may have many apps open which can possibly cause the slowdown and possibly the loss of wifi. In iOS 4-6 double tap your Home button & at the bottom of the screen you will see the icons of all open apps. Close those you are not using by pressing on an icon until all icons wiggle - then tap the minus sign. For iOS 7 users, there’s an easy way to see which apps are open in order to close them. By double-tapping the home button on your iPhone or iPad, the new multitasking feature in iOS 7 shows full page previews of all your open apps. Simply scroll horizontally to see all your apps, and close the apps with a simple flick towards the top of the screen.
 Cheers, Tom