Sheaths are a good thing for men to try if they are left with permanent (mechanical) incontinence as a result of RP, before they take the step of considering an artificial sling, etc. At 4 months post-op, you are still in the stage of recovery - the NHS data suggests that most men see progress between 3-6 months post-op and that 90% of men are using one pad or less by 12 months. Wearing a sheath may give your brain no motivation to re-learn the signals for bladder control and how to control the external sphincter.
Sheaths may also be useful for a short time for a man who normally wears pads but for some specific reason can't, like going to an important meeting or on a long journey. Around the house, I guess there aren't many reasons but perhaps if you were going to the supermarket and you know that their public toilets are closed so you wouldn't be able to change your pad if soaking wet, a Conveen might be sensible.
Our specialist recommended that the pump should be used in 5 x blocks, three times each day.