Is it always safe / reasonable to replace a power supply brick with one rated for more amps?
Is it always safe?  No.   It is usually safe?  Yes.  

There are some characteristics of a power supply that will effect how you use it.

Minimum Load:  A regulator, even a linear regulator, will have a minimum load.  Below this load the power supply will not regulate the output as well.  Sometimes the output will be +/-10% instead of +/-2%.  Other times the output will be way out of whack.  Generally speaking (but there are always exceptions), a power supply rated for a higher max output will also have a higher minimum load.  You might get into trouble if the new supply has a higher minimum load than the old supply.  

Quiescent Power:  This is the power that just the supply is consuming, separate from the load and separate from the supply efficiency.  Bigger supplies generally have higher quiescent power, and that means that the supply will generate slightly more heat.

Efficiency:  Switching supplies generally have the highest efficiency at about 80-90% of the rated max current.   If you get a bigger supply and now you are somewhere near 50-60% of the max current then you are likely running at a lower overall efficiency-- which means more heat.  If you are putting this supply into a chassis that is designed for less heat, you could have problems.

Usually, these issues are not major and you will be safe using a larger supply.  But, you must consider these other issues, just in case.