We have three iPads in our family: our older daughter just bought the new one last year (not the mini--the one before that), I have a 2, and our younger daughter has a 1. The 1 is at least 5 years old, mine is around 2 years old, and the new is about a half year old. We've never had a minute's trouble with any of them. Apple computers are extremely well made, so I expect they'll all keep trucking along for quite a while to come. Yes, they may need new batteries installed one of these days, but that's no big--take 'em to apple, pay the tariff to get the work done, and I'm sure they'll work--and work very well!--for a good many years to come.
iPad was built for the very best of performance and extreme quality with one goal: to make the best 'tablet' in the world. And it happened. And iPad's all Aluminum and Glass enclosure (regardless of what iPad you own) was made with precision to ensure the best of quality. iPad has a legendary 10 hour battery, which works harmoniously with the A4, A5, A5X or A6X chip in your iPad to bring the best of battery health, durability, software protection, and everything else. So given, iPad will definitely last long.
Taking care of iPad is also a priority. That's why all iPads come with 1 year of AppleCare Technical Support and 90 days of Complimentary Phone Support.
I have the original iPhone Witch has to be about 6 years old at the least and I have only a few problems with it the battery dies quick sometimes other times it charges itself somehow so any where from 4 - 8 years
It really does depend of how much you to take care of your 'iPad.' The reason why is because if you didn't take not that much care for your iPad it will break faster than actually taking care for your iPad. If you took Good Care for your iPad then it will last quiet a long time. Let's just hope you take Good Care of your iPad. :)