I don't know if this has been addressed already, but who's to say my priest can't cast spells an infinite amount of times per day, as long as I just keep rolling to curry favor all day?

My party would be at full health all the time. Nobody would ever go into a combat wounded, and as long as I can keep currying favor all day, I can eventually roll enough hammers and boons to cure everyone's critical wounds as well. In fact, there wouldn't be a point in rolling at all. A GM could just assume that, eventually, I'll roll enough hammers to heal everyone.

Suddenly there's no fear of being hurt, or even death, except by that one lucky blow that does ya in.

Is there a limit to how many times a character can be magically healed in a day?

A character can only be healed once from each source in one day. The rule is on page 89 of the Player's Guide under healing limitations. So you cannot spam blessings, spells, first aid or even healing draughts, as they will only work once for each source of healing.

Yes, it's mostly true, except that you can only benefit from one particular healing spell, ONCE per day. Unlike D&D, where you can spam up the Cure Light Wounds forever, in Warhammer, you can only 'benefit' once per day.

Now, if you've got a priestess of Shallya in the group, good for you guys. You deserve to have endless healing. For everyone else, best of luck..GMs quickly become wise to this.

Another element that should be emphasized is that OUT of encounter mode, you're really only making one or two checks. Downtime from the rules is called Story Mode. This is where the GM says, no way.

Anyways, I'd probably allow endless spells if I were playing Lure of the Liche Lord (a dungeon crawl in the wastes of the border princes), just to keep things moving. Otherwise, rules as written

As they said, the Player's Guide clarifies that you can only be healed by each spell or blessing once per day.

Even without that, fear of death isn't completely gone. Sure you could (prior to the Player's Guide) heal repeatedly outside of combat, but a single large battle would be likely to overwhelm the healer's ability to respond fast enough.

That said, I'm really glad the rules-hole got plugged.

EDIT/ADDENDUM:

A GM could just assume that, eventually, I'll roll enough hammers to heal everyone.

The problem with that assumption is in the stars. Wizards trying it would eventually get bit by a really bad miscast. Even many of the Shallyan blessings have amusing/dangerous Chaos Star lines.

My party would be at full health all the time. Nobody would ever go into a combat wounded, and as long as I can keep currying favor all day, I can eventually roll enough hammers and boons to cure everyone's critical wounds as well. In fact, there wouldn't be a point in rolling at all. A GM could just assume that, eventually, I'll roll enough hammers to heal everyone.

And you (the GM) make the process last for many many hours while it happens "off-screen", and the PCs miss their appointment with the important NPC, or they are stuck at the inn 'healing' while the goblin warband that they were supposed to stop went and rampaged through the village, or the bad guys acquired the artifact that the group was trying to get. Etc.

The GM has many tools at his disposal, and is in charge of the story.