i've been there, done that! my tank is close to being what i call complete, and just going to let it grow. I did that with my 30, once i had it all setup with what i wanted, I didnt have to buy livestock or anything but salt and filters for my RO and food. It was quite nice, just wanted something larger this time around.
13 years ago or so, i had too many tanks, too much going on, and had time for nothing else, including a vacation! time came i bought a house, got rid of most of my tanks, (including the 180 i still miss to this day!) and kept a 110 for a while, eventually got rid of it, went about 6 months with nothing, then built an 11g nano i had for 6 years, then the 30 for 2 1/2, and now my 90.
moral of my story:
keep 1 tank, large enough not to take up too much weekly/daily maintenance time, and keep it a hobby, not an obsesion!