What do you define as a 'bad payer'? I've customers who don't pay for 3 or 4 months, but they always cough up, so I think these are good payers.
You have to be able to turn over an amount that far exceeds what you need to live to allow for cash flow problems (IMO).
Also, collecting is a pain, though I still do it for about 40% of my work which is compact. The rest I just leave envelopes or invoice.