Can you have too many? = no.
However
once you have enough for your needs, what you can do is get more discriminating in how you earn them, and what deals you pass up on. I still avidly collect, but only when it is great value to do so. I also still enjoy the buzz of collecting as a hobby, and gain satisfaction from knowing that I can do so better than most. The family certainly enjoys the perks !!!

have just booked SQ in J for next July School holidays for for 3 from MEL-CDG_FRA-MEL. Will shortly book for eldest daughter to return in J from Togo next February.
With still a balance of several million in various accounts while I am still very much an active
points runner, I only now collect those points that are "free" or very low cost in $ + time to collect. I pass up on quite a number of opportunities as I do not need the points, but if I was low in balance would take them as it would still be vastly cheaper than actually having to buy a long-haul fare (
shudder..horror!!!!!). My balance still grows faster than I can spend despite redeeming long-haul J (and occasional F) for a family of five with one or two international holidays per year.
A bit of cunning keeps the points rolling in though. ie My Woolworths grocery spend I gain 3 Amex points and am averaging over 4 QFF Points per $ spent there since the scheme came in and i the main only buy items on sales or at clearance, thus also save $$$ up front......I just pick off the best deals, walk several cards.....and avoid points on most full price promos as I can normally gain a better deal by only buying on sale/clearance.
Having a large spend does allow indulgences. For example for one of my daughters friends I said that if she paid me for the price of economy tickets, that I would supply a Business Class Seat on flights to MEL- Singapore- Cairo- Amman- Johannesburg - MEL. (Note that I also paid the taxes out of what she paid me...and was the main reason I asked that she pay the economy price)