In my opinion, you have arrived at that time. I've been taking generic sinemet and amantadine for the entire time after I was dx'd in 2001, and I have never been sorry. I struggled with depression for more than 15 years prior to PD Dx (still take antidepressants), but after beginning carbidopa/levodopa (sinemet), I experienced the greatest antidepressant effect ever. Of course I can't guarantee you will respond in that way, but, hey, low dopamine can't be helping your mood.
I also take a variety of other things, among them, dextromethorphan (approx. 4 mg at bedtime in cough syrup with no other active ingredients), CoQ10, multivitamins and minerals, and a supplement elixir containing resveratrol and other plant polyphenols.
At this point I take a total of 700mg carbi/levo, 600 of which is CR, each day, and I maintain an essentially normal level of activity for a 72-year old.
As we all know, we are all different, and I can't presume that what has worked for me will be good for you. Just wanted to chime in with my experience.
Robert