A very large empirical study in Google's datacenters was conducted about the reliability of hard drives, and the study analyzed temperature as one of the variables that affected mean time between failure (MTBF), expressed in the article as Average Failure Rate (AFR). The paper is an interesting read, and if you study it carefully, you will gain some detailed insight into how various factors affect the expected lifespan of a hard disk.
However -- if you're looking for an unscientific answer, any temperature within a few degrees of the cited recommended operating temperature -- 0 to 60 C as you say -- should be "fine". You can expect typical failure rates with temperatures within the recommended operating temperature of the drive. You can expect steadily increasing failure rates with temperatures outside of the recommended operating temperature, either at the high or low end.
Since you're well within the operating temperature recommendations, I wouldn't worry about it.
A very salient passage from the paper suggests that temperatures near the high end of the recommended operating range are not high enough to cause a measurable increase in failure rates:
In the lower and middle temperature ranges, higher temperatures are not associated with higher failure rates. This is a fairly surprising result, which could indicate that datacenter or server designers have more freedom than previously thought when setting operating temperatures for equipment that contains disk drives. We can conclude that at moderate temperature ranges it is likely that there are other effects which affect failure rates much more strongly than temperatures do.
I can also correlate these findings with my own personal experience. I have had a dedicated server in a hosting company's datacenter for over two years, and the four HDDs have been on 24/7 since it was installed brand new.
They are bog standard SATA 3GB/s 2TB Seagate hard disks -- not Enterprise-grade. I saw the temperatures in SMART and asked the datacenter about it, but they said that all their drives run at or near that temperature due to the design of the airflow in their datacenter, and that they still have very good MTBF for that model of disk. They told me that the RAID mirroring would protect the data, that they monitor the disk health and will replace a broken disk ASAP, and that they usually get disk failure earlier because of many head parking cycles or because of manufacturing defects, NOT because of temperature.
The disks run at 58 C and not a one of them has failed yet, nor does SMART display signs of pre-failure.