For regular remote access users, recurring payment solutions make sense. Your payment card or payment system account gets charged regularly (monthly, once in 3-6 month or annually), so you have guaranteed access to the service. However, if you are not using the service (or even no longer need it), you will be charged anyway. Examples: LogMeIn Pro, LogMeIn Rescue, SkyFex, DeskRoll, Techinline.
It may be the most cost-effective payment option. Everything depends on the pricing and the licensing policy. If the vendor offers per session payments, this can be very expensive. If you can pay for short periods of unlimited use – that’s often the best way to buy. Examples: Techinline.
Normally, they are very expensive. Often not an option for a startup company or a small business. Examples: TeamViewer.