Very common. Playing a ii-V with no I happens for two main reasons and they're related.
The first is back cycling. Back cycling occurs when you have successive ii-Vs that are separated by a tone or a semitone. By far the most common back cycle is iii-VI7-ii-V7-I. Although this is commonly (and correctly) understood in that form, it can also be correctly interpreted as being a back cycle on the ii-V7-I of the key. This alternate interpretation is useful for analyzing another common back cycle: #iv-VII7-iii-VI7-ii-V7-I. The inclusion of the #iv-VII7 in the progression forces the tune (and later the soloist) to, in a short period of time, address the #4 and the #2.
Back cycling is still somewhat common, but it was far more prevalent in bebop. Behold, the back cycle blues:
BbMaj7 | Ami7b5 D7 | Gmi7 C7 | Fmi7 Bb7
Eb7 | Ebmi7 Ab7 | Dmi7 G7 | Dbmi7 Gb7
Cmi7 | F7 | Dmi7 G7 | Cmi7 F7
The most famous example of these changes is Parker's Blues for Alice. People don't play this so often any more; there are lots of reasons for this, but probably the biggest one is that as solos became slower and more lyrical in the post-bebop era, one bar back cycling to modify the key slightly became less and less relevant to creating interesting solos. When people were blasting out hundreds of notes a minute, the back cycle was a good way to get the solos to follow a contour.
A far more general use of the ii-V without the I is tonicization. Tonicization is differentiated from modulation: whereas modulation is the changing of one key to another, tonicization is the suggestion of one key while staying, in the long term, in the original key. Imagine if you will two (very hokey) chord progressions:
C | Fmi7 Bb7 | Eb | % |
C | Fmi7 Bb7 | C | % |
In the first example, we've clearly moved on to Eb. There's a tonic and it would be silly for us to suggest, while sitting on Eb for two bars, that we're in anything but Eb. In the second example, because we're smart jazz musicians, we know that Fmi7 Bb very strongly suggests Eb, but because we're going to C, we're not in Eb; we're somewhere in between. It is necessary to not simply continue playing in C -- that would be horrible -- but so too would be resolving to Eb, since the notes that make for a good resolution to Eb don't make for a good resolution to C nor do they work over Bb7. The result is that you're somewhere in between changing keys and not changing keys, and your note selection needs to suggest that.
That's a whole different kettle of fish, though. Harmony-wise, what's important to note here is just that ii-Vs with no corresponding Is are sometimes used to suggest another key.
NB: There is considerable overlap between back cycling and tonicization. Look at the example I used earlier. In Bb: Emi7b5-A7-Dmi7-G7-Cmi-7-Bb. In this case, Emi7b5-A7 fits the criteria for both tonicization and back cycling, since it is a tone away from a subsequent ii-V and it suggests a key that you aren't currently in. While it completes the ii-V-I with Dmi7, that Dmi7 goes directly to G7 and is therefore better understood not as a tonic but a subdominant.