I can not give you an personal experience, but one of my coworker's dogs had her first cycle at 7 months. So it is not too early. Sorry I can't be more help. I think there was another post about this earlier. Try doing a search.
My father's dogs (Irish Setters) went into heat about twice a year, so about every 6 months.... But a heat, or season as they are also called, can last up to 21 days. I don't know about Maltese because I have male , I heard it could be anywhere from 1 week to 21 days. But it could be a little unpredictable for the first few heats. Hope this is some help.
We have had experience with this in the past year. 8Mos is not and uncommon thing our vet said with small dogs the first heat can be anywhere from 7-12 months. The heat cycle lasts apx. 21days the bleeding is usually in the middle of this time. I know with our little girl I didn't even know at first she was in heat because she kept herself so clean, it was luck we saw it. As others have said usually around the later part of the heat she is very likely to get pregnant. We did have an oops teen pregnancy as I have shared before. We used the cute little pants (just to keep the boy away, not because of excessive bleeding) and everything and let her outside to go potty, and was not quick enough before our little boy got her ughhh. She was at the tail end of the heat cycle apx day 14-17 so watch her like a hawk h34r: . Happily the bleeding does not last long. She may be a bit moody :wacko: lovable one minute, isolation the next :wacko: Good luck with your little one.