They do fine on their own
We leave our 3rd cat (our paranoid schitzofraidycat) at home for weeks at a time with a neighbor girl checking on her about every 3rd day. We have 2 gravity feeders and 2 gravity waterers, but so far she has never had to refill any of them.
Before our oldest cat was diabetic, we would leave the two of them home together. Now, we have to take the diabetic cat with us to give him his daily shots and feed him his (expensive) special diet.
John W. Irwin
2005 Classic 28 "Sabre-Dog III"
2013 Silverado 2500HD Duramax/Allison LTZ
WBCCI #9632, TAC TX-10