Not all texts are ever received. I had a gent on his way once, text me 3 times while traveling to see me. I never once got any of his texts!!!! And he showed me all 3 of them and it was sent to my number.
I used to prefer only text. I hate talking on the phone, nothing personal, I don't even talk to my mother on the phone. But after that day I realized that calling and speaking with the person is the best way.
Email is great too... but can be lost. I like all appointments set up via email bc I put them into a colander. This way when you need/want a vouch, I can go back and recap our visit.
As far as what is acceptable time frame to text/call/email back... well I guess that is totally up to you. On average you should allow 60-90 minutes. For example. I, myself, never book back to back; however after each meeting (typically an hour give or take, I don't clock watch and have gone over time when really enjoying the apt) I clean up the bedroom, shower, and put away any drinks/towels/empty the trash etc. so that takes typically another 30 mins or so depending on if a crazy hurricane came through.