When you use a SPICE model from the likes of LT based on their design, it models absolutely everything. It has been derived by the engineers who designed the part and used in their extensive testing before being released to the markets. Before the design goes to the chip foundry it has to be spot on design wise. Otherwise it would not be a SPICE model and could cost them a fortune if they got it wrong.
This is a relatively complex part so the simulation can take time. Not like a simple transistor with a transfer function depending on input and output parameters. It has feedback and transient properties to be taken into account.
I recently did an LT SPICE simulation using several of their TIMERBLOX ICs. What appeared to be a simple 'logical' design took over three hours to run the simulation. However, when I finally built the electronics I had designed, it worked first time to as far as I could tell with absolute precision. Just like the simulation had shown. Voltage levels, pulse widths and frequencies to better resolutions what I could measure.
That's the price you pay and it would have been a damn more expensive design had I had to redo the PCB with different build standards regarding components and different topologies.
LT SPICE is probably one of the best simulation packages I have come across (without layout type of restrictions) and don't forget...it's free.