Depends on how symptomatic you are. If its bad, than yes that's too long.
Basically you'll just need to follow your doctor's advice, as well as your own sense of how you are doing. A stress test is basically going to look for three things: ischemia, arrhythmia, and blood pressure response. They'll be looking to see if your heart is still getting enough oxygen when the oxygen demand increases with exercise, as well as to see if your heart produces any potentially dangerous abnormal rhythms during exercise, along with considering if your blood pressure rises appropriately in response to exercise. If you've had high blood pressure for many years then some mild LVH is generally pretty normal and expected. You may or may not have coronary artery disease (basically "clogged arteries") as someone your age with your history of hypertension, family history, and being overweight may be more prone to having, but there's no direct connection between your having some mild LVH and CAD. You're probably pretty much fine to wait and do what you want, but obviously if your doctor has said to hold back then hold back, and if you feel symptoms (for reasons aside from taking a new medication) then pull back. If you're simply worried and want to hold back your activity level as a precaution then you should do that. There are no guarantees in life, but it's unlikely you have any major issues. Your LVH just reflects you being an upper-middle aged person who had high BP for several years. It, yes, makes you less well off than someone without it, but in and of itself it doesn't indicate that your any sort of ticking time bomb or anything of that nature, far from it. That being said, like I said earlier, there are no guarantees in life, so there could be more severe underlying issues, but the point is that nothing you know so far provides evidence of such.
Sorry, meant to say: How long is too long to wait to have a stress test and a echocardiogram?