How often do we need to pray for the Souls in Purgatory?

The 30-day Novena for the Souls in Purgatory teaches that we need to pray more often for our departed friends and loved ones and not only once a year on All Souls Day, November 2 as most of us do.  In my family's case, we do it Quarterly, during the months of : February, May, August and November.  The month of May falls inside the summer school vacation...it is the time when my kids are able to join the full 30-Day Novena prayer.
As mentioned earlier, a short supplication for the souls is included during my family's daily prayers. Aside from this, we include them in the daily 3 O'Clock Prayer to the Divine Mercy.  Each Monday too, we offer special intentions for them in one of the Special Masses for the Souls in Purgatory held at our local cemetery's Chapel. There are four(4) masses each Monday starting from 2pm until 5pm.  From our 400plus name-list, we pick-up 20 names in sequential order  and have them included in the mass. An added list for special intentions, ie. death anniversary, birthdays, respond to special messages/encounters are offered too. There is also an additional list which include my close family members like my parents, grandparents, parents-in-law, uncles, aunties, my late Bro, Samuel, my daughter,Ria(miscarriaged after 2.5 months...please offer a short prayer for her) and newly departed friends and loved ones.
After the mass, I would find time to visit the common burial place of my late family members where I light candles and offer more prayers.