Airplay Timeout Issue

[SoundHound]

I'm having problems with Airplay on my iPad - it works fine until I pause a track. When I resume playback the sound is played through my iPad speakers rather than the Airplay device - I have to select the Airplay device all over again. To an extent, this has always happened, but recently it seems the "timeout" period has reduced significantly. Ideally I'd like to lock the Airplay to my HiFi device until another App needs to use it. Any Ideas welcome thanks.