Our by-laws call for two year tems to the 4 officer positions and states that you can be re-elected is the members want to vote for you. There are no set limits.
Our PTO does have a term limit of two years also with this exception, "an officer can run for more than two terms with a majority vote from the executive board". Luckily that was in place because last year after begging for new officers no one wanted to step up and run for an office.
Our Board Officers can only serve a two year term in any one office. It is conceivable that a person could be Pres for two years and then be Secretary for a year, an possibly continue on. It mixes things up and keeps positions covered if no one steps forward to serve.
2-year term? Sure, if that's what your membership has decided is best for your group. Some groups like to ensure turnover, so that new leaders can be continually cultivated. It's up to your group.
You need to get some dads involved. I have been involved in PTO for 4 years and the dad involvment is growing which is great. One thing that we do is have all our meetings at night. The executive board meets just before the general meeting. Before I was involved the executive board met during the school day and the general meeting was at night but since I work this was not good so a change was made. There are some schools in the district that will only meet during the day thus keeping many dads and working moms out of PTO, this is a shame. We have also been lucky to keep our 4 board members. In the past if one drops out, we would just pick up the slack and work through it but resently we have not lost anyone.