As far as we know, the first 8-9 years of life is the time when visual maturation takes place. That is why we patch during this time period. At age 30, most likely there would not be any benefit to patching the good eye. The lazy eye has improved as much as it can by this time.
As far as improving the vision some other way, if this is truly a lazy eye, there is no other treatment. If the eye is bad for some other reason, there might be treatment available depending on the cause.
Hope this helps.