I just got a new machine because my 37 year old Viking which has sewn miles and miles over the years had a foot controller issue and it was difficult to get a part for it. I will continue to use it for my back up machine. I have two Featherweight machines that are going strong, one from 1934 and the other from 1938 so machines can last a long time if given proper care and you can still get parts for them.
My hope for you is that you have more than 20 years left of sewing. You are relatively young and at your age should be looking more at 30-40 years of sewing. I have several ladies in my quilt guild that are in their 90's and still going strong, driving themselves there and sewing up a storm. In all probability, a machine you buy in your 40's is not a forever machine.