As with most general consumer products, this question is difficult to give a concise answer to. There are too many variables that come into play to answer, such as one year, two years, etc. It all comes down to how you use the gloves, how often you use the gloves, and how durable the manufacturer made them, to begin with.
The latter is something that you need to research, but the other two factors are solely dependent on you. If you are using your touchscreen gloves past their intended designed use (for example at the workplace where you constantly lift heavy objects), they may not last as long as they would if they were used solely for your touchscreen and in the winter.
Then, it also matters how frequently you use the gloves. If you use them every single day for all tasks, then they will not last as long as a pair that is just used occasionally.