To quote the NS documentation: "Note that the filters argument in nlapiSearchRecord(type, id, filters, columns) refers to either a search filter list (nlobjSearchFilter[]) or to a search filter expression (Object[]). With the object reference returned, you can then use any of the following nlobjSearchFilter methods to filter your results." So basically, it is limited by size, but that's almost theoretically unless you are actually pushing a lot of and I mean "a hell lot of" filters.