A: It probably is just a run of bad luck, but you're right to wonder. So here are a few beady questions you should put to yourself.
Fledgling companies put unusual demands on PAs: they're asked to be procurement officers, switchboard operators, corporate communications executives, catering managers and recruitment consultants, as well as dealing with all the e-mails, bills, bookings, insurance, couriers and minicabs. So - are you sure you're not asking too much of them?
Your second PA left for a better job. Did you find out exactly why it was better? Was it just the money, or was the job itself more rewarding? What did you learn?
Since you started this company yourself, you're probably quite happy to work ridiculous hours seven days a week. Founders tend to be obsessive people, who put their private lives on hold for months at a time. Are you expecting your PA to do the same?
Are you expecting a lot and giving too little in return? I don't mean just money: I mean genuine involvement in the business, asking advice and listening to it, sharing goals, setbacks and triumphs.
Fledgling businesses can be hugely attractive to certain kinds of people and deeply unnerving for others. When next you interview a potential PA, do your very best to discover which of those categories she - or he - seems to belong to.