I too would like to use consecutive giving years in donor acknowledgement letters in Mail instead of calculating "donating since..."  using first gift date.  The use of consecutive years data is much more impactful and engaging from a donor's perspective.

Do you mean in the "Fields to Include" tab to be able to show what a donor has given in multiple years (whether it be fiscal or calendar year)? I know it would be helpful for my organization since we like to send our Thank You Letters showing what they have given in 2017, 2016, and 2015 separately. Currently, you can only add one summary amount for the Calendar Year, Fiscal Year, or specific date.