so what you exactly wanna do?
add pets with different durations? like for 1 day - 1 week etc (or custom count) like 20 days
there should be in cashshop .cfg files and cashshop folder config setttnigs for x shop items which if u understand these files u ccan experiment and make it happen, im not sure if its in SQL.. in SQL u can set duration, not sure where but in some Pets table / stored procedure for sure.