The thing that affects us the most is extended bath time.  
 
Crissy is my little fireball . . . my inside fence jumper, my outside fence escapee, my cuddler, my sweet girl. 
Carter is my the oldest but keeps up with Crissy in playing.  He doesn't escape outside, doesn't jump inside fences and is the same as he's always been. 
Cooper is just like my daughter (he's her yorkie).  He loves to sleep, is too lazy to open the doggie door and go outside (we have to open it for him), could care less about escaping but loves to chase birds.   
Cooper moved out for a few months but he and my daughter both moved home about 2 weeks ago.  Before Cooper moved out, it was he and Carter that would snuggle, play together, etc.  Now that he's back home . . . he just chills out while Carter and Crissy play. 
Doesn't seem that anything stays the same as to which two pair up.  Regardless . . . they are all special!  So what that it takes longer to bathe them or more money to feed them or more money to care for them at the vet's office or more doses of heartworm and flea meds.  They are simply a joy!