You asked if it is necessary to keep the software on your hard drive. Keep it or do not keep it--up to you. Print paper copies for your records---or do not print them.
"What if he forgot to save them.....what if a meteor strikes.....etc. etc. etc......"
If you used desktop software downloaded/installed from a CD to your own computer, then the tax files are stored locally on your own hard drive or any backup device you used like a flash drive. They are not stored online. If you cannot recover them due to a hard drive failure, etc. you can get a free transcript from the IRS or for a fee of $43, an actual copy of your tax return.
https://www.irs.gov/individuals/get-transcript
https://www.irs.gov/pub/irs-pdf/f4506.pdf
You want backward capability---not a bad idea. Just giving you the reality as it is right now and trying to answer the question as to whether keeping the software on your computer for years is absolutely necessary.
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**
