Worth going from R49 to R60 in attic?
The answer is it matters, barely.   

Beyond R25 in most climates has very very diminishing returns.  Having air seal to the house and air flow in the attic is way more important than adding more insulation.   

I don't want to get into a diatribe but thermal mass (think weight of your building) is a much better indicator of energy savings than insulation.   Adding insulation on normal wood framed homes allows heat (or cold) to store in the insulation thereby negating the effectiveness beyond the "blocking".   

You can use a calculator to do the numbers and for a 1000 sq ft house you are looking at around $7-10 a year... and remember this calculator does not account for the mass of your home (or lack of) and it is actually created by the insulation industry - so they are going to use the lab numbers that suit them best.

When insulating your attic - taking other things out - there are three main things:


Don't expose wood that touches the house - wood is really a poor insulator so cover it.
There has to be a thermal break.   So is there a defined area of a few inches that covers everything from everything touching your "ceiling".
Does the quantity ensure if there are low spots that there is still proper coverage.


Look at the picture below.   Once you get to the "R40ish" stage, yes more is better, but does it have any sort of lasting effect?   No.