INN members are encouraged to set the defaults on online donor pages to monthly gifts, sometimes called sustaining donations. If possible set your donation page so the default amount and frequency are for monthly gifts, with an easy check-box or toggle if someone wants to switch and make a one-time donation instead. Monthly gifts generate more revenue over time and strengthen donor relationships. For more:
Five Reasons Why Every Nonprofit Needs a Sustained Giving Program (2015, npENGAGE)
Top 5 Reasons to Invest in Monthly Recurring Donations (Classy.org)
Why Monthly Giving Is Good… for Donors (2015, Re:Charity)