If I were you, it would be a question of a- does it do what I need it to do and b- does it get the most current OS/security updates. You’ve said it does what you need it to, and a 2018 MacBook Pro should run latest macOS Sonoma so b is ticked too. I’d hang onto it. It might not get the next version of macOS and if not, it will get security updates for a while longer. I’d look to sell it around then and buy whatever M series MacBook I could afford.
If I were you, it would be a question of a- does it do what I need it to do and b- does it get the most current OS/security updates. You’ve said it does what you need it to, and a 2018 MacBook Pro should run latest macOS Sonoma so b is ticked too. I’d hang onto it. It might not get the next version of macOS and if not, it will get security updates for a while longer. I’d look to sell it around then and buy whatever M series MacBook I could afford.