We bought in 2007. Our house more than doubled in price since then. I’m not sure I could afford to buy it now if I was a typical 20% down buyer.
In your case (assuming $300K original house price) you will sell it for $600K, net $264K profits after commissions. Use profits plus $60K of original downpayment and any additional equity in the old house as a downpayment for a similar house at $600K. The new mortgage will be similar to one you had in 2007. Same rate and most likely smaller principal. Not a big difference.
The problem is that I'd be taking on a new 30-year mortgage while being about 10 years away from retirement rather than ~26 years away from retirement, which has certain implications on my ability to afford that mortgage over its full term.
Statistically very few people stay at the same house for 30+ years, most move within eight.