What version of FileMaker 12 are you using? 12.0v4? (Pull down help and check the "About" option)
Yes, it is 12.0v4.
Switching layouts IS slower in FileMaker 12--especially in the initial versions, which is why I asked if you had 12.0v4--the latest reelase which is much faster than the original release. And the delays can be very platform sensitive. My new W7 laptop with a faster processor and lots of RAM pops from layout to layout in nice, snappy fashion. The xp box with less RAM and a slower processor that I have here at work, is many times slower.
But 3-5 minutes seems very extreme for this.
Try creating a small test layout with just a few records and simple layouts. Do you see the same delays on it?
If not, you'll need to investigate the design of your database to see if you can isolate what is slowing things down to such an extreme degree.
Possible factors to investigate:
Scripts performed by triggers when you change layouts.
Conditional formatting--especially if they refer to aggregate values (Sum, average, count...) from a related table or summary values from the current table. And also if you have a large number of conditionally formatted objects on your layout.
Unstored calculations that access aggregate values from related tables or from summary fields in the layout's table...
One trick to try is to use duplicate layout to copy your layout and then try removing a design detail you suspect of being responsible for the delay. Since you are testing a copy of the layout, you can delete the layout and work from a new copy to test how much different aspects of your design affect system response times. You can also, of course, test completely separate copies of your file for the same reason.
Once you can narrow this down to one or a few factors, we can take a clearer look at whether there is a way to modify the design so that things work faster for you in FileMaker 12.