IDC: Software vendors chart licensing sea change. Software makers are moving toward subscription-based licensing, as changing demands from customers dictate a shift from the paradigm of a one-time sale with upgrades, says a research report. Some 43 percent of the 100 software vendors polled by IDC believe subscription licenses will represent the majority of sales in six years time. [CNET News.com]
[via Scott Young]

If you were going to sell software for say $40 and offer free upgrades, you could instead sell the software for $27.50 and have the software require a new license after 18 months.  Sacrificing some short-term revenue for long-term revenue. 

Some users may like this,  others won’t.  Perhaps you will always have to offer multiple choices.