For most of my clients in this situation we just suppress estimates.  If their income is fairly stable there's a very good chance they'll fall under one of the other underpayment exceptions (i.e. 90% of current year income).  It's ultimately their decision but I make a recommendation based on the situation and tell them that if anything changes significantly to let me know and we can do a mid-year projection.

I do have several clients with stock options/restricted stock which causes their income to vary pretty wildly from year to year and in those cases we do aim for the 110% safe estimates/increased withholding.  So really you just have to assess the situation, inform your client of the ramifications and make an appropriate recommendation.  There's not always a "one size fits all" solution.

Rick