If you believe that Network Solutions will be around and in the domain business long term, you can have them handle it for you.
They offer 20 and 100 year "registration". I put registration in quotes because the max underlying registration is still only 10 years. They implement 20 and 100 year registration by registering for 10 years and then extending that one year per year.
The 100 year "registration" used to even be a good deal. It was $999, which for .com and .net and .org brought the effective per year price down to around what the cheaper registrars charged and locked it in.
I actually thought of using it for my domain, until I remembered that I'll be long dead before getting anywhere near even half of that time out of it. Even taking into account likely price increases in year by year registration at the cheap places, which make the break even point for $999/100 years much earlier than 100 years, I was unlikely to be around that long.
100 years is now $2000, making it a much less interesting deal. Still, assuming a modest annual increase at the cheap registrars it still does eventually win so if you are going to need the domain a long time it might actually be worth it (if you are confident NS will last that long), and does make it so you don't have to think about the problem for another 100 years.
The 20 year option, also for $20/year, is almost certainly not worth it unless not having to worry about renewal for 20 years is an overwhelming concern for you. The prices at the cheaper registrars are probably unlikely to rise fast enough to make the break even for $20/year less that 20 years out, assuming you start with a 10 year registration now so that the current ~$10/year is locked in for 10 years.