Internally-heated external rollers transfer heat rapidly to a fuser roller in an electrostatographic printer. Stored media process set points, input image content and input media type data are used to regulate the heat transfer rate by varying the nip width between the heated external rollers and the fuser roller. The rate of heat transfer and the rate of heat transfer adjustment are sufficiently rapid that many different media weights and types may be mixed in a print run without restrictions on media run lengths, without collation requirements per run, and without productivity losses due to slowing of feed rate for heavier receivers.