You can use L=2u , provided there are no restrictions from the foundary on Maximum Channel length and no change in device performance with this large L.
for analog , we tend to use non-minimal channel length , however , depending on the fab , it may characterize only for certain channel length i.e. from 0.18u to 0.5u , it is all depend on the charaterization proceedures for a certain fabs, there may be fabs that provide a full characterization to a large range of channel lengths, also , it may put limits to the size of your design
if ur doing RFIC design u should use the minimum length such in LNA use minimum length
but for ordinary analog , like BG , OPAMPS current mirror use multiples of minimum length