Is it normal for any dog to urinate just once daily?

I have a year and a half old pug; she's wonderful. Anyway, she is starting to pee (one long pee) just once daily. She had a problem with urinating several months ago. I left for a week and left her in good hands with my older son (we both love her dearly but she knows that she is mine) and she developed crystals in her urine tract. She didn't pee for two days after I got home so I called the vet and went in. She needed anti-biotics and luckily her crystals cleared up. She usually pees atleast twice daily but the past 2 days it's been only once. Should I call the Vet tomorrow for her to be seen? Ours never just gives advice/answers; they all want to see the animal. Is once per day even if it lasts a while ever enough for your doggie to go pee? Thank You................Should I wait for another day or two to see if her urination increases? Of course if she stopped, even for one day, I would get her to the vet. Thanks