Hi, I'm soon to be 64 and tow a 25' Surveyor SP220. I tow at 60 mph most of the time and find that speed and that length of trailer is my comfort zone. The Mrs. and I don't feel the need (yet?) for a bigger trailer; maybe later after she retires (she's 52 and I've already medically retired, she hasn't retired). I guess for me age isn't the factor so much as what you are comfortable towing or driving safely.
2013 Forest River Surveyor SP220 Sport
2012 Ram 1500 4X4, 5.7L Hemi quad cab