Margaret —

Sorry for the lateness of the reply.

There is no maximum age for the obligation of attending Mass. There are no hard and fast rules about who is excused and who is not. If it is not feasible to attend because of infirmity, you are excused. What I would offer is that:

• If you are seeking an excuse not to attend because you do not wish to attend, then you ought to make every effort to go, and I'd encourage you to read a good devotional booklet on the value and power of the Eucharist (such as Beautiful Eucharist, edited by Matthew Kelly).
• If, on the other hand, you want with all your heart to go, but find it is just not feasible, then you have a good excuse not to go.
  

Remember that people have risked their lives in certain times and places just to attend Mass they considered it so precious, so we should avoid being cavalier about excusing ourselves. But there are legitimate excuses.

Eric