Gregg Ludwig <<gregg.ludwig.cfi>>
writes:

As a refresher or reminder for aerotow tug pilots, in addition to
obviously being a proficient pilot, 61.69 requires currency. Meeting currency
required by regulation is easy and is similar to meeting landing currency where
that requires 3 logged t/o and landings within 90 days to carry a passenger. 
Tug pilot currency is typically overlooked with FAA ramp checks but most hang
glider competition administrators will ask for documentation. Like landing
currency the tug pilot currency does not require an endorsement. A note in your
logbook (by you) stating that you are current through (state date) should
suffice. Shown here is currency requirement from 61.69:

(6) Within 24 calendar months before the flight has—

(i) Made at least three actual or simulated tows of a glider or unpowered
ultralight vehicle while accompanied by a qualified pilot who meets the
requirements of this section; or

(ii) Made at least three flights as pilot in command of a glider or unpowered
ultralight vehicle towed by an aircraft.

Notice that aerotowing as a solo tug pilot does not meet the requirement towards
currency (but does provide proficiency). For tug pilots that also hang glide it
probably easiest to list some hang gliding  aerotows in your logbook. If
you took 3 hang gliding (aerotow) flights in one (1) week you would be current
for almost two (2) years.