Can SQL Server's Page Life Expectancy be too high?
No, I can't think of any situation or theory in my head that could illustrate a negative side effect for an astronomically high PLE (unless you enjoy the humming sound of the platters in a hard disk drive?).

With memory getting cheaper and cheaper, and buyers-of-hardware getting a little more generous, these bigger memory boxes we see it is quite common to have PLE in the thousands upon thousands range.  It's simply one indication that your instance may not be under memory pressure.  Take it for what it is, and only that.

Page Life Expectancy is just an estimation SQL Server makes on how long it thinks a page will last in a buffer.  This is SQL Server's way of saying it thinks it'll be "a while".

Another thing of note, take Paul Randal's advice and don't concentrate on the PLE reported by the buffer manager.  Like all averages, the buffer manager can hide differing PLEs.  You want to look at all of the individual NUMA nodes' PLEs with the Buffer Node counter:

Get-Counter -ListSet "*" | 
    Select-Object -ExpandProperty Counter | 
    Where-Object {$_ -like "*buffer node*page life expectancy*"} | 
    Get-Counter


Page Life Expectancy is simply one color in the beautiful painting that is SQL Server memory.  Look at it along with the other "colors" (target/total server memory, available mbytes, etc.).  Too often people look at one simple metric and fear either their server is about to explode, or conversely that it'll live for centuries unmanaged.