A lifespan of a tensile membrane structure is dependent on the budget of the project. The budget determines what design and materials are needed for the construction of the tensile membrane structure. For instance on fabric roof systems, there are several fabric types with corresponding lifespan. Silicon coated glass fibre fabrics and ETFE, PTFE fabrics, PVC coated with PVDF fabrics can make it from 20 to 50 years. Some PVC and HDPE Shade Cloth fabric on the other hand can make it 5 years to 15 years. You can check a full list of fabric types and characteristics on TE Membrane Material Comparison Table.
The budget is the key on how long a tensile structure will last. If the budget is too tight, materials with lesser quality is an option. Some companies tend to go for cheaper materials which may not last longer than expected and compromise the technical requirement of the fabrics.