No, it doesn't. I got 3.9 Gb Maps on SD-card and have a start up time of appr. 12-14 seconds.
CAUTION: Avoid having GPX files on the SD-card. If you have them there, the Unit ALWAYS has to parse the gpx files which leads to those long start up times.
Gpx files (especially large cache gpx files) should always be copied onto the unit.
HTH
Hans