It's 200 hours if you feel like spending extra money o­n it, via external batteries. Right off the shelf, it gets 40 hours from the included NiCds.
No OGG support yet...other details inside.

Matsushita Electrical Industries Corporation will release the "SL-CT510" MP3 supporting portable CD player o­n February 10th. Though officially Open Price, indicators suggest it will cost around 10,000 yen. There are 4 different color variations: Silver (-S), Blue (-A {as in, "aoi" I guess}), Pink (-P), and Yellow (-Y).
[1]
The SL-CT510 is the successor to the "SL-CT500" portable CD player released by the same company back in February of 2003. {The new unit} supports CD-R/RW, and playback MP3 files - but there was no display of ID3 tags o­n the included LCD remote control.

Although it is a basic model, it features things like a digital amp, high quality in-ear headphones, and during MP3 playback, can also interpolate music that was cut during the compression process via the "Digital Re-Master" function.

Also, to control the amplifier's levels from becoming too excessive, it will automatically adjust them using the featured "D-AGC" (Digital-Auto Gain Control). To suppress distortion, it also includes the previously featured "S-XBS" for emphasizing low (bass) tones, as well as even moreso with "S-XBS+" allowing bass to be experienced to the greatest extent.

Furthermore, in addition to the 4 audio modes offered by "S-XBS" and "S-XBS+", users can also select from 8 different surround effects: "Hall," "L-Hall," "Air," "Club," "L-Club," "Float," "Space," and finally "Stage."

Power comes from 2 AA size NiCd rechargeable batteries, with a total recharging time of 2.5-3.5 hours. Also, when used with the external battery case and 4 alkaline batteries, up to 200 hours (MP3 disc) of constant playback are possible.

Battery Continuity Time